PROPOSALS FOR A REVISED CLASSIFICATION SYSTEM FOR
CALCAREOUS NANNOPLANKTON
We have recently been working on a new version of A Stratigraphical Index of Calcareous Nannofossils (Bown, in press).
During this work we needed to address the question of the classification of nannofossils, and attempted a comprehensive
generic-level review. We had originally intended to publish this in the book but space constraints prevented this. In addition,
since one of the problems of classification is a lack of consensus, it seemed sensible to proceed on a broader basis. So,
following consultation with various INA committee members, we decided to publish a working draft classification here ingood time for subsequent discussion at the Puerto Rico INA Conference, at which we will host a workshop during which thefollowing papers will be thoroughly discussed. Eventually, it is our intention to publish a final version of these papers,
incorporating the results of these workshop discussions, as a handbook which will be distributed to all members of the INA.
We have set out the classification in three separate papers. First, a discussion of the higher-level approach adopted and its
relationship to previous classifications, followed by separate sections on Mesozoic and Cenozoic nannofossils. The
Mesozoic/Cenozoic divide follows the precedent of Perch-Nielsen (1985a, b), and for much the same reasons: most majorgroups are predominantly confined to one era or other, so that grouping Mesozoic and Cenozoic nannofossils together intaxonomic sequence results in awkward alternations between the two eras.

Acknowledgements: Thanks to Katharina von Salis, Jackie Burnett, Liam Gallagher, Matt Hampton and Kevin Cooper forcomments and discussion at various stages of this work.
Paul Bown & Jeremy Young

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HIGHER CLASSIFICATION OF CALCAREOUS NANNOFOSSILS
Jeremy R. Young, Palaeontology Dept., NHM, Cromwell Road, London, SW7 5BD, UK &Paul R. Bown, Dept. of Geological Sciences, UCL, Gower Street, London, WC1E 6BT, UK

Classification development
The starting point for this overview was the comprehensive review and classification of nannofossils of Perch-Nielsen(1985a, b), complimented by, in particular, the Jurassic nannofossil classification of Bown (1987, 1996) and theclassification of extant haptophytes by Jordan and co-workers (Kleijne, 1993; Green & Jordan, 1994; Jordan & Kleijne,
1994; Jordan & Green, 1994; Jordan et al., 1995). Important earlier sources for these classifications include Parke & Dixon(1976), Hay (1977), Okada & McIntyre (1977) and Tappan (1980). In order to provide a comprehensive synthesis, we paid
special attention to taxonomic papers published since 1985, as catalogued in the INA Bibliography and Index of Taxa. For
the Tertiary, the reviews of Aubry (1984 et seq.) were invaluable sources, although they are based on a slightly different
taxonomic philosophy.

Top-down subdivisions vs bottom-up groupings
Two main approaches can be identified in the classification of calcareous nannofossils. The top-down subdivision approach
has attempted to classify the range of nannofossils into well-defined subdivisions using clear-cut criteria based on major
aspects of shape or structure. For instance, Deflandre (1950) divided all nannofossils into ortholiths and helioliths based onwhether they showed radial calcite orientations (helioliths) or were formed of single calcite crystals (ortholiths, including theconstituent segments of pentaliths). The bottom-up grouping approach, by contrast, has been based on organisation of
species into genera and of genera into families based on multiple similarities of morphology, existence of intergradational
morphologies and stratigraphic distribution. The latter, bottom-up, approach is, we believe, more productive and leads to amore natural classification, and it is the predominant method applied in Perch-Nielsen (1985a, b). This forms the basis for
our formal classification into genera, families and orders. The top-down subdivision approach is, however, valuable fororganising taxa of uncertain inter-relationship and so we apply a system of this type to arrange the higher taxa we recognise
in a logical sequence, and in some cases to provide arbitrary subdivisions of particular taxa.

Incertae sedis and informal categories
A key objective of classification is to systematise our existing knowledge. Conversely, an obvious pitfall of classification isto provide, via spurious pigeon-holing, the impression of knowledge where none exists. To avoid this we have attempted to
discipline ourselves and only to include genera within families (or families within orders) where there is good positive
evidence for doing so. As a consequence, the classification is not comprehensive - many genera are left as of uncertain
family/order, and many families are not assigned to an order. We do not apologise for this, since it is a simple reflection of
the limits of current knowledge.

Use of orders as well as families
The only higher taxonomic category which has been universally applied is family and we continue to use families as themain level of classification. However, in revising the classification, we considered that exclusive use of families was unduly

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restrictive and that, with around 50 families, important relationships would be obscured.
We decided to use orders (Figure 1), rather than to subdivide families, in order to retain as many taxa as possible at theircurrent level, the alternative being to reclassify many well-established families as subfamilies. Also, orders have previously
often been used in nannofossil classifications, notably by Hay (1977), Tappan (1980) and Bown (1987). The principle
potential problem here is discordance with use of orders in the classification of modern haptophytes. Classifications ofmodern haptophytes have, following Parke & Green (in Parke & Dixon, 1976), usually recognised four orders:
Coccosphaerales (coccolith-bearing), Prymnesiales (typical non-coccolith-bearing haptophytes, haptonema well developed),
Isochrysidales (haptonema diminutive, including some coccolith-bearing genera), and Pavlovales (with the flagella ofunequal lengths, the longer flagellum with hairs and scales, haptonema diminutive). Recent work on molecular genetics,
cytology and biochemistry, have unequivocally established the distinctive nature of the Pavlovales and they are now
separated as a discrete class or subclass (Green & Jordan, 1994). The subdivision of the remaining haptophytes into theother three orders has not, however, been supported by subsequent studies, with the result that Green & Jordan (1994)
recommended subsuming all these orders into the single subclass Prymnesiophycidae, order Prymnesiales. Given thisabandonment of the traditional ordinal-level classification of extant haptophytes there is no obvious problem in introducing
a new ordinal-level classification based in the first place on coccolith morphology, although obviously future research on
aspects of haptophyte biology is liable to result at least in modifications of this classification. Nonetheless, this is not an area
where we are especially dogmatic, and debate on use of particular levels of classification would be welcome.

Paraphyletic and polyphyletic taxa
We have not attempted to avoid paraphyletic taxa, i.e. taxa which give rise to other taxa of the same, or higher, level (Figure2). For instance, according to our current understanding of coccolithophore phylogeny, the family Zygodiscaceae isparaphyletic since it is inferred to have given rise to the families Pontosphaeraceae and Helicosphaeraceae. Similarly, thegenus Lophodolithus is paraphyletic if we accept the interpretation that it gave rise to the genus Helicosphaera and family
Helicosphaeraceae. This is manifestly an unavoidable problem in nannofossil systematics since we have abundant evidenceof ancestor-descendant relationships. To give an extreme example, the genera Praeprinsius, Prinsius, Toweius,
Reticulofenestra, Gephyrocapsa, and Emiliania are widely inferred to constitute an evolutionary lineage (e.g. Romein, 1979;
Gallagher, 1989) and so all these, except Emiliania, are paraphyletic.
On the other hand, it is clearly essential to eliminate polyphyletic taxa, i.e. all species included in a higher taxon must have acommon ancestor within that taxon (Figure 2). This is an absolute necessity of a biologically meaningful classification - ifavailable evidence suggests that a taxon contains unrelated sets of species then it must be revised. Of course, we often do notknow for certain whether a group of more or less similar species is directly related or simply a set of convergent
homeomorphs. All taxonomic groupings may be regarded as hypotheses which may be tested through analysis ofmorphology and direct evolutionary data. Our general approach has been to avoid giving taxonomic names to any
subdivisions which we feel are likely to be polyphyletic, for instance we have followed Kleijne (1991) in dividing the large
number of extant holococcolith-bearing genera into two groups based on whether they show dimorphism or not. However,since this character is very likely to have evolved repeatedly, it does not form a suitable basis for grouping the genera into
formal taxa.

Heterococcoliths, holococcoliths and nannoliths

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A special problem with nannofossil taxonomy is the uncertainty as to whether the structures we are examining arehomologous. Indeed, we know that holococcoliths and heterococcoliths are not homologous, whilst we are uncertain as tothe nature of nannoliths. This requires some discussion, and in addition there are separate taxonomic problems associatedwith each of these groupings.

Heterococcoliths
This is the predominant group, usually defined as coccoliths formed of a limited number of complex and variably shaped
crystal-units. The precise scope of the term heterococcolith is vague but there is no dispute that the term is based on typicalextant coccoliths such as those of Coccolithus, Emiliania, Pleurochrysis and Syracosphaera (see also original description ofBraarud et al., 1955). These all share the basic morphology of a rim formed of a radial array of complex crystal-units
surrounding a central-area, with variable structures in the central-area. This basic morphology characterises numerous living
and fossil groups and forms an essential part of most workers' concept of an heterococcolith. There is also evidence that thisis a natural, non-polyphyletic, grouping: (1) studies of evolution in the group tend to indicate a pattern of common origin
and subsequent divergence, with no obvious indications of polyphyly (e.g. Bown, 1987; Romein, 1979; Bown et al., 1992);(2) our ultrastructural research (Young & Bown, 1991; Young et al., 1992; unpublished data) suggests that a widespread,and probably universal, feature of heterococcoliths is V/R mode biomineralisation, i.e. biomineralisation which commenceswith nucleation of a proto-coccolith ring of alternating subvertical and subradial crystal-units, which subsequently develop
to form the rim. This type of biomineralisation is characteristic of all the heterococcolith families recognised here except
possibly the Rhabdosphaeraceae (only V-units definitely identified), Hymenomonadaceae and Papposphaeraceae. V/R modebiomineralisation is a distinctive and sophisticated type of calcification and it seems reasonable to assume that it is a reliable
synapomorphy (shared derived character state), and that the heterococcoliths as a whole form a non-polyphyletic group.

Holococcoliths
Holococcoliths are plainly formed by a very different biomineralisation process to heterococcoliths. Nucleation must occur
across the entire coccolith and the individual crystals retain simple euhedral morphologies. As a result, there is no clear
distinction between the rim and central-area. Moreover, available evidence suggests that calcification occurs extra-cellularly(Rowson et al., 1986), rather than intracellularly. Finally, there are now several well-established cases of holococcoliths andheterococcoliths occurring on alternate phases of the life-cycle of single species. Billard (1994) synthesises this evidence
and suggests that it reflects a haplodiplontic life-cycle, with holococcoliths consistently occurring in the haploid phase. Thisrather suggests that biomineralisation may have evolved independently in the haploid and diploid phases, and that
holococcoliths and heterococcoliths are not meaningfully homologous (Figure 3). Possibly we should consider holococcolithand heterococcolith taxonomy as independent, much as spore and whole-plant taxonomy are.

Holococcolith biomineralisation is distinctive and sophisticated. Crystallite faces are perfectly aligned across large zones,
implying precise control of both a- and c-axis orientation, and the uniformity of crystallite size implies similarly precise
control of nucleation spacing. Like V/R mode biomineralisation in heterococcoliths, it is unlikely that the holococcolithbiomineralisation mode has evolved repeatedly, rather we can regard holococcolith formation as evidence for common
descent of all taxa in which it is developed. Plainly though, both holococcolith formation and heterococcolith formation may
have been lost repeatedly during the evolutionary history of haptophytes. So there is no reason for assuming that all

Nanno classification, JNR 4

holococcoliths will have heterococcolith-bearing phases, or that all species which are known to have both holo- andheterococcolith-bearing phases will be particularly closely related. Future research will certainly help elucidate
relationships. In the interim, it is entirely logical for all holococcolith bearing taxa, without known heterococcolith phases, tobe classified together, in the family Calyptrosphaeraceae.

Unlike heterococcoliths, holococcolith biomineralisation does not provide obvious characters for reliably subdividing thegroup. Homology is difficult to establish since the basic structure appears to consist of a simple mass of crystallites, grossmorphology appears to be of limited value, and there are serious problems due to dimorphism. So at present,
subclassification of the Calyptrosphaeraceae is confined to a rather unsatisfactory, and probably partially artificial, genericclassification. This applies particularly to extant holococcoliths for which crystallographic orientations are poorly known. In
the larger fossil holococcoliths, subdivision into blocks with predictable crystallographic orientations appears to provide a
reasonable basis for classification, but original morphology and possible dimorphism cause separate problems.

Nannoliths
When Braarud et al. (1955) defined the terms heterococcolith and holococcolith, they explicitly described the pentaliths as athird category of similar status. This was a logical proposal since pentaliths show different structures to any heterococcoliths
and it is reasonable to infer they have formed by a significantly different growth/biomineralisation process, and therefore are
not directly homologous. The same applies to numerous other groups, particularly amongst the extinct nannofossils, e.g.
sphenoliths, nannoconids and discoasters. The term nannoliths has been widely used as a collective term for this group (e.g.
Perch-Nielsen, 1985a, b; Bown, 1987; Aubry, 1984 et seq.; Young et al., in press). The most common definition iscalcareous nannofossils of uncertain affinity, but probably related to coccolithophores, i.e. formed by haptophytes.

Although nannoliths are highly variable, several features are repeatedly shown: (1) most nannoliths have morphologies
which are at least suggestive of having been part of a composite exoskeleton; (2) most nannoliths are formed ofmorphologically-complex crystal-units analogous to those of heterococcoliths, although in some cases with evidence ofadditional ultrastructure (e.g. laminae within pentalith crystal-units); (3) for all known nannoliths there are consistent
relationships between morphology and crystallographic orientation; (4) most nannoliths definitely show consistent
handedness or chirality (deviation from radial symmetry), e.g. nannoconids always show clockwise imbrication,
Braarudosphaera sutures are always offset clockwise from the median point of the pentalith edge; (5) nannoliths typicallyhave biogeographic patterns suggesting planktonic origin and as a group are only known from the Triassic to Recent.

These features all suggest close affinities with coccolithophores. Moreover, haptophytes are the only plankton group known
to produce calcareous scales. Dinoflagellates also calcify but they form calcispheres rather than discrete scales. Various
other phytoplankton produce scales, e.g. Prasinophytes and Chrysophytes, but these are either unmineralised or siliceous.
Hence, an assumption that nannoliths are produced by haptophytes has seemed reasonable to phycologists and has been
supported by independent evidence in several cases, e.g. association of ceratoliths and coccoliths (Norris, 1965; Alcober &Jordan, 1997), observation of haptonema on Polycrater (Thomsen et al., 1994), LM observations of typical haptophyte cellfeatures for Braarudosphaera (J. Green, pers. comm., 1996).

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Nannoliths as a whole are, however, almost certainly polyphyletic, probably including: (1) modified heterococcoliths(?Florisphaera, ?polycycloliths, ?helioliths, ?fasciculiths, ?sphenoliths); (2) modified holococcoliths (?ceratoliths,?Lithostromationaceae); (3) and nannoliths formed by entirely different biomineralisation mechanisms (?pentaliths,?Polycrater, ?nannoconids). So they cannot be regarded as a formal taxonomic group, even though it is extremely useful todistinguish them from the more rigorously definable holo- and heterococcoliths. Further research will probably allow someto be reclassified as aberrant heterococcoliths or holococcoliths, whilst others may prove to be discrete groups.

Formal higher classification
The haptophytes were traditionally included in the phylum Chrysophyta along with a range of other golden-brown, scalebearing algae. However, Parke et al. (1955) recognised the haptonema as a unique structure, and following this they wererecognised as a distinct class by Christensen (1962) and division by Hibberd (1972). Rather unfortunately, Hibberd (1976)
argued that the name Haptophyta was unsuitable since it was not based on a generic root. He proposed the alternative name
Prymnesiophyta, and this name was widely used in the literature until recently. However, as noted by Green & Jordan(1994), under the International Code of Botanical Nomenclature, division-level names do not need to be typified and thename Haptophyta has priority. Following from this, the common term haptophyte is preferable to prymnesiophyte; it is also
a less forbidding term so we expect it to rapidly regain universal currency.

Notwithstanding this nomenclatural confusion, the separation of the haptophytes on the grounds of flagellar character has
been well supported by much other evidence from cytology, biochemistry and molecular genetics. There is no dispute thatthey form a discrete algal protist group separable at division/phylum level. Chloroplast colour, however, reflects rather
fundamental aspects of pigment biochemistry, e.g. green algae and land plants all have chlorophyll a and b. By contrast,
golden-brown algae, including haptophytes, have chlorophyll a and c. This unites them with a range of other non-green
algae, including the diatoms and silicoflagellates. Another common feature of this group is that the chloroplasts are
surrounded by four membranes, which is interpreted as the result of a complex endosymbiosis history. Finally, most of thesegroups have two flagella, one short and smooth, the other long and bearing tubular hairs (heterokont). On the basis of this setof shared characters, Cavalier-Smith (1981, 1994) has proposed removing the group from the Protista to form a separate
kingdom, Chromista, also including various protozoa which show the same heterokont flagellation. The haptophytes, as
noted above, have two smooth flagella, and so do not show heterokont flagellation, hence their position in this group issomewhat uncertain, but the general interpretation is that they are a primitive group that diverged prior to the evolution ofheterokont flagellation (e.g. Cavalier-Smith, 1994).

Within the haptophytes, only the single class Prymnesiophyceae is now recognised, divided into two subclasses, thePrymnesiophycidae and Pavlovophycidae (see Green & Jordan, 1994). All coccolithophores belong to the
Prymnesiophycidae, and so to:

Kingdom CHROMISTA Cavalier-Smith, 1981
Division (Phylum) HAPTOPHYTA Hibberd ex Cavalier-Smith, 1986
Class PRYMNESIOPHYCEAE Hibberd, 1976
Subclass PRYMNESIOPHYCIDAE Cavalier-Smith, 1986

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Layout
The same format has been adopted for both of the following papers. For each genus, the original authorship is given,
followed by important synonyms in brackets (). There are then short notes outlining the basis for distinguishing the genus.
Terminology used in these descriptions follows Young et al. (in press). In some places we have included genera which arearguably redundant, and these are placed in square brackets [].

The formal systematic classification is supplemented, as seems useful, by informal groupings. These are numbered andgiven in bold. In most cases, these subdivisions are arbitrary and are likely to prove artificial/polyphyletic, hence they are
not proposed as the bases for future formal classification.

Constraints of space meant it was not practical herein to provide a complete bibliography of taxonomic references. The
references can, however, be found in Perch-Nielsen (1985a, b), and/or the INA Bibliographies.

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References
Alcober, J. & Jordan, R.W. 1997. An interesting association between Neosphaera coccolithomorpha and Ceratolithus
cristatus (Haptophyta). European Journal of Phycology, 32: 91-93.
Aubry, M.-P. 1984 et seq.. Handbook of Cenozoic calcareous nannoplankton. Micropaleontology Press, American Museumof Natural History, New York. Book 1: Ortholithae (Discoasters), 266pp. (1984). Book 2: Ortholithae (Catinasters,
Ceratoliths, Rhabdoliths), 279pp. (1988). Book 3: Ortholithae (Pentaliths, and others), Heliolithae (Fasciculiths,
Sphenoliths and others), 279pp. (1988). Book 4: Heliolithae (Helicoliths, Cribriliths, Lopadoliths and others), 381pp.
(1990).
Billard, C. 1994. Life cycles. In: J.C. Green & B.S.C. Leadbeater (eds). The Haptophyte Algae. Systematics Association
Special Volume, 51, Oxford University Press: 167-186.
Bown, P.R. 1987. Taxonomy, evolution, and biostratigraphy of Late Triassic-Early Jurassic calcareous nannofossils. Special
Papers in Palaeontology, 38: 118.
Bown, P.R. 1996. Recent advances in Jurassic calcareous nannofossil research. Georesearch Forum, 1-2: 55-66.
Bown, P.R. (ed.) In press. Calcareous nannofossil biostratigraphy. British Micropalaeontology Society Series, Chapman &Hall Limited.
Bown, P.R., Burnett, J.A. & Gallagher, L.T. 1992. Calcareous nannoplankton evolution. Memorie di Scienze Geologiche,
43: 1-17.
Braarud, T., Deflandre, G., Halldal, P. & Kamptner, E. 1955. Terminology, nomenclature, and systematics of the
Coccolithophoridae. Micropaleontology, 1: 157-159.
Cavalier-Smith, T. 1981. Eukaryote kingdoms: seven or nine? BioSystems, 10: 93-114.
Cavalier-Smith, T. 1994. Origin and relationships of Haptophyta. In: J.C. Green & B.S.C. Leadbeater (eds). The Haptophyte
Algae. Systematics Association Special Volume, 51, Oxford University Press: 413-436.
Christensen, T. 1962. Alger. In: T.W. Böcher, M. Lange & T. Sorensen (eds). Botanik Bd 2, Systematisk Botanik, Nr. 2,
Munksgaard, Copenhagen: 1-178.
Deflandre, G. 1950. Observations sur les Coccolithophoridés, à propos d'un nouveau type de Braarudosphaeridé,
Micrantholithus, à éléments clastiques. Comptes Rendus de l'Academie des Sciences, 231: 1156-1158.
Gallagher, L.T. 1989. Reticulofenestra: A critical review of taxonomy, structure and evolution. In: J.A. Crux & S.E. van
Heck (eds). Nannofossils and their applications. Ellis Horwood Limited, Chichester: 41-75.
Green, J.C. & Jordan, R.W. 1994. Sytematic history and taxonomy. In: J.C. Green & B.S.C. Leadbeater (eds). The
Haptophyte Algae. Systematics Association Special Volume, 51, Oxford University Press: 1-22.
Hay, W.W. 1977. Calcareous nannofossils. In: A.T.S. Ramsay (ed.). Oceanic Micropaleontology. Academic Press: 10551200.
Hibberd D.J. 1972. Chrysophyta: definition and interpretation. British Phycological Journal, 7: 281.
Hibberd D.J. 1976. The ultrastructure and taxonomy of the Chrysophyceae and Prymnesiophyceae (Haptophyceae): a
survey with some new observations on the ultrastructure of the Chrysophyceae. Botanical Journal of the Linnaen
Society, 72: 55-80.
Jordan, R.W. & Green, J.C. 1994. A check-list of extant haptophyta of the world. Journal of the Marine Biological
Association of the United Kingdom, 74: 149-174.

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Jordan, R.W. & Kleijne, A. 1994. A classification system for living coccolithophores. In: A. Winter & W.G. Siesser (eds).
Coccolithophores. Cambridge University Press: 83-106.
Jordan, R.W., Kleijne, A., Heimdal, B.R. & Green, J.C. 1995. A glossary of the extant haptophyta of the world. Journal of
the Marine Biological Association of the United Kingdom, 75: 769-814.
Kleijne, A. 1991. Holococcolithophorids from the Indian Ocean, Red Sea, Mediterranean Sea and North Atlantic Ocean.
Marine Micropaleontology, 17: 1-76.
Kleijne, A. 1993. Morphology, taxonomy and distribution of extant Coccolithophorids (calcareous nannoplankton). PhD
thesis, FEBO, Enschede, The Netherlands, Vrije University, Amsterdam: 321pp..
Norris, R.E. 1965. Living cells of Ceratolithus cristatus (Coccolithophorinae). Archiv für Protistenkunde, 108: 19-24.
Okada, H. & McIntyre, A. 1977. Modern coccolithophores of the Pacific and North Atlantic Oceans. Micropaleontology, 2:
1-55.
Parke, M. & Dixon, P.S. 1976. Check-list of British marine algae - third revision. Journal of the Marine Biological
Association of the United Kingdom, 56: 579-604.
Parke, M., Manton, I. & Clarke, B. 1955. Studies on marine flagellates. II. Three new species of Chrysochromulina. Journalof the Marine Biological Association of the United Kingdom, 38: 579-609.
Perch-Nielsen, K. 1985a. Mesozoic calcareous nannofossils. In: H.M. Bolli, J.B. Saunders & K. Perch-Nielsen (eds).
Plankton Stratigraphy. Cambridge University Press: 329-426.
Perch-Nielsen, K. 1985b. Cenozoic calcareous nannofossils. In: H.M. Bolli, J.B. Saunders & K. Perch-Nielsen (eds).
Plankton Stratigraphy. Cambridge University Press: 427-554.
Romein, A.J.T. 1979. Lineages in Early Paleogene calcareous nannoplankton. Utrecht Micropalaeontological Bulletins, 22:231pp..
Rowson, J.D., Leadbeater, B.S.C. & Green, J.C. 1986. Calcium carbonate deposition in the motile (Crystallolithus) phase of
Coccolithus pelagicus (Prymnesiophyceae). British Phycological Journal, 21: 359-370.
Tappan, H. 1980. The paleobiology of plant protists. Freeman & Co.: 1028pp..
Thomsen, H.A., Buck, K.R. & Chavez, F.P. 1994. Haptophytes as components of marine phytoplankton. In: J.C. Green &B.S.C. Leadbeater (eds). The Haptophyte Algae. Systematics Association Special Volume, 51, Oxford University Press:
187-208.
Young, J.R., Bergen, J.A., Bown, P.R., Burnett, J.A., Fiorentino, A., Jordan, R.W., Kleijne, A., van Niel, B.E., Romein,
A.J.T. & von Salis, K. In press. Guidelines for coccolith and calcareous nannofossil terminology. Palaeontology, 40.
Young, J.R. & Bown, P.R. 1991. An ontogenetic sequence of coccoliths from the Late Jurassic Kimmeridge Clay of
England. Palaeontology, 34: 843-850.
Young, J.R., Didymus, J.M., Bown, P.R., Prins, B. & Mann, S. 1992. Crystal assembly and phylogenetic evolution inheterococcoliths. Nature, 356: 516-518.

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Figure 1: Proposed heterococcolith orders. Sketches illustrate distal views, and side-views with interpreted cut-away crosssections. Vertical thickness of cycles is sometimes exaggerated to clarify structure.

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Figure 2: Holophyletic, paraphyletic and polyphyletic taxa.

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Figure 3: Diagram showing how current observations on haptophyte life-cycles can be resolved into a consistent phylogeny.

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MESOZOIC CALCAREOUS NANNOPLANKTON CLASSIFICATIONPaul R. Bown, Dept. of Geological Sciences, UCL, Gower Street, London, WC1E 6BT, UK &Jeremy R. Young, Palaeontology Dept., NHM, Cromwell Road, London, SW7 5BD, UK

Abstract
We present herein a revised three-level order-family-genus classification for Mesozoic calcareous nannoplankton. Two neworders (Arkhangelskiales, Stephanolithiales), five new families (Axopodorhabdaceae, Kamptneriaceae, Lapideacassaceae,
Tubodiscaceae) and one new combination (Zeugrhabdotus sigmoides (Bramlette & Sullivan, 1961)), are introduced.

Introduction
The purpose and philosophy of this contribution are explained in the introductory section (Young & Bown, above). A threelevel order-family-genus classification is used, as far as seems reasonable, based on current knowledge. In addition, a set of
numbered groupings (1. Heterococcoliths to 3. Nannoliths) are used to provide a logical, but very possibly artificial,organisation, particularly of families and genera incertae sedis. Question marks preceding generic names indicate tentative
inclusion in the family.

1. HETEROCOCCOLITHS
1.1. Murolith coccoliths
Description: Wall-like rim, typically higher than it is wide, composed of two crystal-units: the distal/outer cycle (V-unit),
which is commonly dominant; and the proximal/inner cycle (R-unit), which is subordinate and sometimes vestigial. The
light microscope (LM) cross-polarised light (XPL) image is either bicyclic, with a dark outer cycle and a bright inner cycle,
or unicyclic and relatively dark. This image variability is dependent upon the size of the proximal/inner cycle and theorientation of the rim, i.e. whether it is vertical or flaring.
Remarks: The division between the two murolith orders proposed herein, is based upon orientation of the elements in the
distal/outer cycle, i.e. imbricating or non-imbricating. This distinction is apparent and stable through most of the Mesozoic
but may be less clear amongst some Upper Triassic and Lower Jurassic muroliths, which represent the products of the initial
diversification of this group (Figure 1).

1.1a. Imbricating muroliths (loxoliths)
Order EIFFELLITHALES Rood, Hay & Barnard, 1971
Description: Murolith coccoliths with a distal/outer cycle composed of imbricating elements, i.e. in side-view, the sutures
are not vertical. This feature is not distinguishable from non-imbrication in the LM. The distal/outer cycle imbrication isclockwise. The term loxolith is applied to this rim structure (Bown, 1987).

Family CHIASTOZYGACEAE Rood, Hay & Barnard, 1973 emend. Varol & Girgis, 1994
Description: Loxoliths with variably-developed proximal/inner-cycles and a central-area spanned by axial, non-axial or
diagonal crossbars or a single transverse bar which is, however, usually formed from four, fused bars. LM image includes
both unicyclic and bicyclic types.

Nanno classification, JNR 13

Comments: This broad taxonomic group includes numerous simple loxolith forms. This simple model of coccolith
construction was repeatedly modified through the Mesozoic and these subtle and numerous morphological variations arereflected in a taxonomy which is virtually unworkable. Very few distinctive and well-constrained species exist, and mostcommonly-used species names are virtually meaningless form-taxa. Even at the generic level there is no consensus on
nomenclature, illustrated by the following list of names applied to forms with axial crosses: Bownia Varol & Girgis, 1994,
Rothia Varol & Girgis, 1994, Staurolithites Caratini, 1963, Staurorhabdus Noël, 1973, Vekshinella Loeblich & Tappan,
1963, Vagalapilla Bukry, 1969.

A new classification of the group was recently proposed by Varol & Girgis (1994), however, their subdivision is based upon
whether the LM rim image is unicyclic or bicyclic, a feature which appears to be of dubious taxonomic significance and isprobably homoeomorphic within this group. An informal subdivision is applied below.

Central-area axial crossGenus Ahmuellerella Reinhardt, 1964 (= Actinozygus Gartner, 1968){complex axial cross structure or plate, includes 8 axial or radial 'bars'}?Genus Bownia Varol & Girgis, 1994
{type (and possibly only) species, B. mutterlosei, is bicyclic; both cycles highly birefringent}
Genus Bukrylithus Black, 1971
{unicyclic (LM) with broad, fibrous, tapering axial crossbars}
Genus Diadorhombus Worsley, 1971
{type species, D. rectus, has a square-shaped loxolith rim and is probably not related to similarly- shaped
Stephanolithiaceae coccoliths, e.g. Rhombolithion}
Genus Heteromarginatus Bukry, 1969
{bicyclic, additional small bars in the central-area}
Genus Misceomarginatus Wind & Wise in Wise & Wind, 1977 (?= Monomarginatus Wind & Wise in Wise &Wind, 1977){narrow, bicyclic rim; wide central-area with axial crossbars and perforate plate}
Genus Monomarginatus Wind & Wise in Wise & Wind, 1977
{narrow, unicyclic rim; wide central-area with axial, concentric and lateral bars}
Genus Rhabdophidites Manivit, 1971 emend. Lambert, 1987 (= Rhabdolekiskus Hill, 1976){small basal coccolith with axial cross supporting very tall spine}
Genus Staurolithites Caratini, 1963 (= Staurorhabdus Noël, 1973; Vekshinella Loeblich & Tappan, 1963;
Vagalapilla Bukry, 1969; Haslingfieldia Black, 1973; ?Pontilithus Gartner, 1968){practically a form-genus/genera for loxoliths with a simple axial cross}
Genus Vaucherauvillius Goy, 1979
{axial, lateral and concentric bars, span the central-area}

Central-area transverse bar?Genus Archaeozygodiscus Bown, 1985
{Triassic genus, bicyclic (LM) with a birefringent, spine-bearing bar. Distal/outer cycle displays
anticlockwise imbrication, unlike all other Mesozoic loxoliths}
Genus Amphizygus Bukry, 1969 (= Bipodorhabdus Noël, 1970){bicyclic rim; transverse bar formed from laths which continue around the inner edge of the rim, delineating
the two circular perforations. No spine}Nanno classification, JNR 14

Genus Gorkaea Varol & Girgis, 1994
{bicyclic (LM), bright inner cyclic is broad; robust, birefringent, transverse bar; ?junior synonym of
Zeugrhabdotus}?Genus Placozygus Hoffman, 1970
{distal/outer cycle shows little or no imbrication; rim exhibits spiral interference pattern. The common
species, P. sigmoides, is best classified as Zeugrhabdotus}
Genus Reinhardtites Perch-Nielsen, 1968
{unicyclic, very broad rim, with narrow central-area spanned/filled by a bar}
Genus Tranolithus Stover, 1966 (?= Pontilithus Gartner, 1968){central-area spanned by 2-4 broad, disjunct platelets. In T. orionatus, 4 platelets constitute a transverse bar,and there is a proximal net of lateral bars}
Genus Tubirhabdus Prins ex Rood, Hay & Barnard, 1973
{central-area structure supports broad, hollow, flaring spine}
Genus Zeugrhabdotus Reinhardt, 1965 (= Glaukolithus Reinhardt, 1964; ?Gorkaea Varol & Girgis, 1994; Lordia
Varol & Girgis, 1994; Rectapontis Varol & Jakubowski, 1989; Zygolithites Black, 1972; Barringtonella
Black, 1973){uni- and bicyclic forms, with variably constructed transverse bar}
Zeugrhabdotus sigmoides (Bramlette & Sullivan, 1961) Bown & Young comb. nov.
Basionym: Zygodiscus sigmoides Bramlette & Sullivan, 1961 (Micropalaeontology, 7, 129-188, p.149, pl.4,
fig.11a-e)

Central-area diagonal crossGenus Chiastozygus Gartner, 1968
{includes uni- and bicyclic forms with variably constructed diagonal crossbars}

Central-area closed or open with variable bars/grills
Genus Crepidolithus Noël, 1965 (?= Millbrookia Medd, 1979){broad, high rim with central-area vacant, closed or spanned by bars or grill}
Genus Neocrepidolithus Romein, 1979
{broad, high rim with narrow or closed central-area which may be spanned by bars}

Central-area net or vacantGenus Loxolithus Noël, 1965
{broad, open central-area, probably spanned by a rarely preserved, finely perforate net, see Lambert, 1993,
pl. 5, figs 1 and 2 (named Millbrookia perforata therein)}

Family EIFFELLITHACEAE Reinhardt, 1965
Description: Loxoliths with a well-developed proximal/inner cycle and typically a wide central-area spanned by axial, nonaxial (asymmetric), or diagonal crossbars. The broad, proximal/inner cycle is conspicuous in LM, creating a strongly
bicyclic image.
?Genus Diloma Wind & Cepek, 1979{?tricyclic - dark, narrow, inner and outer cycles; bright, broad median cycle; central-area spanned by axial
or near-axial cross, with or without lateral bars}
Genus Eiffellithus Reinhardt, 1965

Nanno classification, JNR 15

{crossbars generally fibrous and spine-bearing; relationship between Neocomian forms, and Albian andyounger representatives uncertain; see Rothia}
Genus Helicolithus Noël, 1970
{narrow central-area, filled by broad, lath-formed crossbars}
Genus Rothia Varol & Girgis, 1994
{alternative name for Neocomian Eiffellithus representatives}
Genus Tegumentum Thierstein in Roth & Thierstein, 1972
{similar to Eiffellithus, however, the inner rim cycle is strongly imbricate and the crossbars are lath- formed
rather than fibrous}

Family RHAGODISCACEAE
Description: Loxoliths with a dominant distal/outer-cycle and a central-area typically filled by a plate of granular calcite.
The central structure may be spine-bearing, perforate or massive. The LM image is generally unicyclic.
Genus Calcicalathina Thierstein, 1971
{central-area filled by a large, domed, granular mass}
Genus Percivalia Bukry, 1969{concentric multicyclic inner-rim construction with granular plate or bar}
Genus Rhagodiscus Reinhardt, 1967 (?= Viminites Black, 1975){central-area filled by a granular plate which may be perforate and spine-bearing}

1.1b. Non-imbricating muroliths (protoliths)
Order STEPHANOLITHIALES Bown & Young ord. nov.
Description: Muroliths with a distal/outer-cycle composed of non-imbricating elements, i.e. in side-view, the sutures arevertical or near-vertical. This feature is not distinguishable from imbrication in the LM. The term protolith is applied to thisrim structure (Bown, 1987). Figure 2 provides a schematic overview for this group.

?Family CALCIOSOLENIACEAE Kamptner, 1927
Description: Coccoliths are rhombic muroliths, usually termed scapholiths. The central-area is spanned by numerous
transverse bars. See Young & Bown (below) for further discussion.
Genus Calciosolenia Gran, 1912 (= Acanthosolenia Bernard, 1939; Scapholithus Deflandre, 1954){small, rhombic muroliths with numerous, parallel transverse bars}

Family PARHABDOLITHACEAE Bown, 1987
Description: Protoliths with high rims and a central-area spanned by an axial cross or transverse bar but commonly filled bybroad, often tall spines. The LM image is usually bicyclic, with the proximal/inner cycle well-developed. Commonly
observed in side-view.
Genus Bucanthus Bown, 1987
{bicyclic (LM), with offset central cross}
Genus Crucirhabdus Prins ex Rood, Hay & Barnard, 1973 (= Apertius Goy, 1979){spine-bearing axial cross, with or without additional lateral bars}
Genus Diductius Goy, 1979
{bicyclic (LM), with central-area grill}
Genus Mitrolithus Deflandre, 1954

Nanno classification, JNR 16

{central-area filled by massive boss/spine}
Genus Parhabdolithus Deflandre, 1952
{central-area filled or part-filled by broad, often tall, spines}
Genus Saeptella Goy, 1979
{central-area axial cross and grill}?Genus Thurmannolithion Grün & Zweili, 1980
{axial cross, lateral bars, and minor longitudinal bars forming a grill}?Genus Timorella Bown, 1987
{modified protoliths, with tapering, cup-like rim and central-area plate}?Genus Umbria Bralower & Thierstein in Bralower et al., 1989
{bicyclic (LM) with granular central-area plate}

Family STEPHANOLITHIACEAE Black, 1968
Description: Protoliths with low rims, weakly-developed or vestigial proximal/inner cycles, and a central-area spanned by
one to numerous bars. Coccolith outline may be polygonal. LM image is usually unicyclic and inconspicuous, although anumber of genera do exhibit bicyclicity, e.g. Rotelapillus, Stephanolithion and Stoverius (Figure 2).
Genus Corollithion Stradner, 1962
{bicyclic, polygonal, usually hexagonal, rim with 4-6 radial bars in the central-area}[Genus Cylindralithus Bramlette & Martini, 1964]{see Watznaueriaceae}[Genus Diadorhombus Worsley, 1971]{type species, D. rectus, has a loxolith rim; see Chiastozygaceae}
Genus Rectilius Goy, 1979
{central-area grill}
Genus Rhombolithion Black, 1973
{diamond-shaped rim; arguably a junior synonym of Stradnerlithus}
Genus Rotelapillus Noël, 1973{high, bicyclic (LM), circular rim with lateral rim spines and 8 radial central-area bars}
Genus Stephanolithion Deflandre, 1939
{bicyclic (LM), elliptical to geometric rim with lateral rim spines and 1-8 central-area bars}
Genus Stoverius Perch-Nielsen, 1984
{broadly-elliptical to circular, bicyclic (LM) rim with central-area cross}
Genus Stradnerlithus Black, 1971 (= Diadozygus Rood, Hay & Barnard, 1971; Nodosella Rood, Hay & Barnard,
1973){inconspicuous (LM), elliptical or polygonal rim with 4 or more central-area bars}
Genus Truncatoscaphus Rood, Hay & Barnard, 1971
{elongate, subhexagonal rim with 6 or more central-area bars}

1.2. Placolith coccoliths
Description: Broad and thin rim, usually constructed from two superimposed, appressed shields joined by a tube-cycle.
Precise understanding of the relationship between rim-cycles is often lacking, but where known, the shields are constructedfrom two crystal-units which may be complexly intergrown and superimposed, leading to a multicyclic, surficial
appearance. LM image is wholly dependent upon the relative development of the two crystal-units (V and R), which isextremely variable, but usually consistent within families. When V- and R-units are relatively equally developed, i.e. each

Nanno classification, JNR 17

forming an entire shield, the LM image is predominantly dark but often bicyclic, the inner cycle being narrow and bright,
e.g. Biscutaceae, Prediscosphaeraceae. When the V-unit is weakly developed, and it is often reduced to peg cycles or isvestigial, then both shields are almost wholly constructed from R-unit crystals and the LM image is bright, e.g.
Watznaueriaceae. Mesozoic placoliths generally have simple, monocyclic proximal shields, which vary little from family tofamily. Cenozoic placoliths have more-complexly constructed proximal shields which are often bicyclic.

1.2a. Non-imbricating (or radial) placoliths and related taxa
Order PODORHABDALES Rood et al., 1971 emend. Bown, 1987
Remarks: This order includes the Biscutaceae and other closely related forms, which have placolith (or modified placolith)
coccoliths with shields formed from elements which display little or no imbrication and, typically, equal development of V
and R crystal-units, i.e. one shield (distal) formed from V-units, the other from R-units (proximal). The V/R development isreflected in consistent LM images which are of low birefringence but high relief in phase contrast. Shield elements are
typically joined along radial sutures, but these may often curve or kink. Element curvature is consistently dextrogyre (veeing
anticlockwise) and obliquity is broadly dextral (clockwise) in the distal shield, and the same in the proximal shield whenviewed proximally.

The rim constructions of the Cretarhabdaceae, Tubodiscaceae and Mazaganellaceae are not well understood, and thesefamilies are only tentatively assigned to this order.

Family AXOPODORHABDACEAE Bown & Young fam. nov.
Type genus: Axopodorhabdus Wind & Wise in Wise & Wind, 1977.
Description: Placoliths with two narrow shields and a wide central-area, spanned by axial crossbars or granular plates withvariable numbers of perforations; the central structure generally supports tall, hollow spines. The distal shield is formed
from V-unit elements joined along radial or near-radial sutures which show little or no imbrication. The proximal shield andinner cycle (if present) are formed from R-units. LM image is generally dark, but bright inner-cycles may be developed. The
image is characterised by clearly visible shield elements, often giving a 'beaded' appearance around the inner edge of theshields.
Comments: We have abandoned the name Podorhabdaceae in favour of Axopodorhabdaceae due to problems associatedwith the type genus of the former family (Podorhabdus, type species P. grassei Noël, 1965). Many authors believe that theholotype illustrations of P. grassei represent a species of Discorhabdus, which should then be classified in the Family
Biscutaceae. It would be extremely undesirable to use Podorhabdus for those coccoliths presently within Discorhabdus, orto use Podorhabdaceae to replace Biscutaceae; the informal term podorhabdid is useful, and widely used, to described thecoccoliths classified together in the Axopodorhabdaceae.
The Axopodorhabdaceae has been dramatically overdivided, with numerous, monospecific genera distinguished only by the
number of central-area perforations (Figure 3). The family requires a species-level review, and revision is not attempted
here.
Genus Axopodorhabdus Wind & Wise in Wise & Wind, 1977
{tall-spine-bearing axial cross}
Genus Cleistorhabdus Black, 1972
{central-area plate with one large perforation/spine base}Nanno classification, JNR 18

?Genus Cribrosphaerella Deflandre in Piveteau, 1952 (= Psyktosphaera Pospichal & Wise, 1990){elliptical to subrectangular rim; multiperforate central-area net}
?Genus Cribrocorona Perch-Nielsen, 1973{high, subcircular rim; narrow central-area with grill}
Genus Dekapodorhabdus Medd, 1979
{10 central-area perforations}
Genus Dodekapodorhabdus Perch-Nielsen, 1968
{12 central-area perforations}
Genus Ethmorhabdus Noël, 1965
{multiperforate central-area net with or without axial cross and spine}
Genus Hemipodorhabdus Black, 1971
{spine-bearing transverse bar}
Genus Hexapodorhabdus Noël, 1965
{bars delineate 6 large perforations, including one at each end of the central area}?Genus Nephrolithus Górka, 1957
{reniform rim; central-area net with 2 to numerous pores}
Genus Octopodorhabdus Noël, 1965
{bars delineate 8 large perforations, including one at each end of the central-area}
Genus Octocyclus Black, 1972{bars delineate 8 large perforations, lying at the sides of a longitudinal bar}
Genus Perrisocyclus Black, 1971 (= Teichorhabdus Wind & Wise in Wise & Wind, 1977; Duplexipodorhabdus
Varol & Girgis, 1992){one or two cycles of central-area perforations}[?Genus Podorhabdus Noël, 1965]{granular central structure with two marginal perforations, supports tall, hollow, flaring spine; see discussionof family}
Genus Teichorhabdus Wind & Wise in Wise & Wind, 1977
{two cycles of small central-area pores}
Genus Tetrapodorhabdus Black, 1971
{diagonal or four offset cross bars}

Family BISCUTACEAE Black, 1971
Description: Placoliths with two broad shields, which may or may not include a distal innercycle (tube-cycle), and a small
central-area which may be vacant, filled with granular calcite or spanned by variably-oriented bars or axial crossbars. The
distal shield is formed from V-units and the proximal shield and tube-cycle are formed from R-units; the distal shieldelements are joined along radial or near-radial sutures (+/- kinks) and show little or no imbrication. LM image is generally
dark, but bright inner-cycles are common. Coccospheres are well known and usually spherical or cylindrical. A diagramatic
overview of the family is shown in Figure 4.
Remarks: The taxonomic significance of conspicuous tube-cycles has led to a variety of classification schemes within thisfamily. In a study of the oldest (Early Jurassic) biscutaceans, de Kaenel & Bergen (1993) proposed considerable revision tothis family. These authors distinguish Palaeopontosphaera (widely regarded as a junior synonym of Biscutum) from
Biscutum by the presence of a birefringent, distal inner cycle. However, the type species holotype (EM) of Biscutum was a
proximal view and thus the presence or absence of a tube-cycle cannot be determined. Moreover, they argue that the

Nanno classification, JNR 19

aforementioned holotype is very nearly circular and emend the genus in such a way as to render it equivalent to Bidiscus
Bukry, 1969 (= Discorhabdus Noël, 1965) (i.e. circular to subcircular, unicyclic placoliths), a drastic change compared to its
normal and widespread usage.

The holotype in question is badly damaged (around 40% is missing) and most probably not lying flat, and it is therefore very
difficult to prove that this specimen is circular. In fact, Black (in Black & Barnes, 1959) clearly states that the holotype iscomposed of "two unequal elliptical discs" (p.325), and discusses at some length the geometrical changes in the shape of therim elements around the ellipse (p.326). We therefore propose that the traditional usage of Biscutum is retained, i.e.
subcircular to elliptical biscutacean coccoliths which typically have a distal, inner tube-cycle. This causes least disruption in
the relatively stable Biscutaceae taxonomy and is as justifiable as the case presented by de Kaenel & Bergen (1993), given
the available evidence. The inclusion of the earliest biscutaceans in the genus Similiscutum is, however, followed here.

The genus Discorhabdus (= Bidiscus) is distinguished on its circular outline. In many coccolith groups, outline is not astable, taxonomically significant feature, however Discorhabdus represents a coherent, long-lived group in which outline isconsistently circular. There are also additional morphological features which distinguish them from the rest of the family,
e.g. most species lack an inner distal tube-cycle and many Jurassic representatives have large spines.
Genus Biscutum Black in Black & Barnes, 1959 (= Palaeopontosphaera Noël, 1965){broadly elliptical-elliptical shields with or without a tube-cycle; the central-area may be imperforate or
narrow and vacant or spanned by a simple structure (cross or bar)}
Genus Boletuvelum Wind & Wise in Wise & Wind, 1977
{Biscutum-like coccoliths with large, hollow, flaring spines, closed distally by a domed covering; may
simply represent well-preserved Biscutum coccoliths (see Hattner & Wise, 1980, pl.4, fig.6; Lambert, 1993,
pl.13, fig.1)}
Genus Crucibiscutum Jakubowski, 1986
{Biscutum-like coccoliths with prominent, birefringent, axial cross}
Genus Discorhabdus Noël, 1965 (= Bidiscus Bukry, 1969){circular rim, generally no central-area structure, but may (Jurassic forms) or may not (Cretaceous forms)
bear a spine}
Genus Gaarderella Black, 1973
{broad shields with wide granular central-area plate; rarely reported}
Genus Gephyrobiscutum Wise, 1988
{bicyclic rim; narrow central-area spanned by an oblique transverse bar; rarely reported}
Genus Seribiscutum Filewicz et al. in Wise & Wind, 1977
{central-area spanned by broad platelets}
Genus Similiscutum de Kaenel & Bergen, 1993
{subcircular-elliptical shields with smooth, grey appearance in LM and a narrow, bright inner-cycle (not a
tube cycle); central-area narrow and may be empty or spanned by an axial cross}
Genus Sollasites Black, 1967 (= Costacentrum Bukry, 1969; Noellithina Grün & Zweili, 1974 in Grün et al., 1974){elliptical, usually bicyclic rim; distinct central-area structure composed of axial cross, multiple longitudinalbars and/or concentric bars. Classified in a separate family or subfamily by some authors}

Family CALYCULACEAE Noël, 1973

Nanno classification, JNR 20

Description: Modified placoliths constructed from a high, broad, flaring distal-shield composed of radial, non-imbricating
elements, and a proximal-shield which is often reduced to a simple, narrow cycle of elements; central-area structures arehighly variable, including numerous bars, concentric structures, nets and grills. The distal shield is formed from V-units andthe proximal shield is formed from R-units. LM image is generally dark, but the high distal shield often shows somebirefringence, reflecting the thickness of the crystals; commonly observed in side-view. There is some evidence of
coccosphere dimorphism (Goy, 1981).
Genus Calyculus Noël, 1973 (= Proculithus Medd, 1979; Incerniculum, Vikosphaera, Catillus Goy, 1979){see description of family}
Genus Carinolithus Prins in Grün, Prins & Zweili, 1974
{extremely modified; trumpet-shaped coccoliths}

Family PREDISCOSPHAERACEAE Rood, Hay & Barnard, 1971
Description: Elliptical to circular placoliths with two shields and a central-area spanned by crossbars which support tall,complexly-constructed spines. The distal shield is typically bicyclic, with a broad outer cycle, usually constructed from 16
non-imbricating elements (V-units) and a narrow inner cycle (tube-cycle) (R-units). The proximal shield is formed from Runits. The LM image is bicyclic, with the outer cycle dark, and inner cycle bright.
?Genus Petrarhabdus Wind & Wise in Wise, 1983
{massive, short, blocky spine}
Genus Prediscosphaera Vekshina, 1959 (= Deflandrius Bramlette & Martini, 1964){see description of family}

Rim structure uncertain but tentatively placed within the Podorhabdales
Family CRETARHABDACEAE Thierstein, 1973
Description: Placoliths with two shields and a central-area spanned by a variety of structures, most commonly fibrous axial
crossbars with subsidiary lateral bars and a solid central spine or process (Figure 5). The distal shield is generally bicyclic,
with a narrow outer cycle and a dominant, broad inner cycle; the elements are usually radial or near radial and do not appear
to imbricate. The relationship between these cycles and the coccolith crystallography is presently uncertain. LM image ismoderately birefringent.
Genus Cretarhabdus Bramlette & Martini, 1964 (= Allemannites Grün in Grün & Allemann, 1975){axial cross and net}
Genus Cruciellipsis Thierstein, 1971 (= Miravetesina Grün in Grün & Allemann, 1975
{broad shields with broad, tapering, birefringent axial cross bars; lateral bars have been reported}?Genus Flabellites Thierstein, 1973
{central-area spanned by small, blocky diagonal cross; outline may be asymmetric}
Genus Grantarhabdus Black, 1971 (= Gephyrorhabdus Hill, 1976){diagonal cross bars}
Genus Helenea Worsley, 1971 (= Microstaurus Black, 1971){distal shield inner cycle displays distinct suture obliquity and ?imbrication; narrow central-area spanned bycrossbars which may bifurcate at their ends and usually support a short, blocky spine}[Genus Microstaurus Black, 1971]{commonly used genus, but a junior synonym of Helenea}
Genus Mirevetesina Grün in Grün & Allemann, 1975
{broad shields, weak axial cross, net; ?early Cruciellipsis}

Nanno classification, JNR 21

?Genus Pickelhaube Applegate, Covington & Wise, 1987
{large, broad, strongly concavo-convex ?proximal shield; narrow ?distal shield; central-area axial cross andlateral bars}
Genus Polypodorhabdus Noël, 1965
{distal shield slopes in to the central-area; axial cross and numerous lateral bars}
Genus Retecapsa Black, 1971 (= Allemannites Grün in Grün & Allemann, 1975){axial cross with lateral bars; some authors include these forms within Cretarhabdus}
Genus Speetonia Black, 1971
{single transverse bar}
[Genus Stradneria Reinhardt, 1964]{holotype drawing shows a weak axial cross and a solid intergrowth of radial laths; name not commonly
used}

Family MAZAGANELLACEAE Bown, 1987
Description: Three-shielded placoliths with a wide central-area spanned by a variety of bars, grills, nets or plates. The distal
shield may be high and flaring. The distal shield is formed from one cycle of non-imbricating elements, joined along radial
sutures; the exact structural relationship between the different shields is unknown at present. LM image is generally dark,
but birefringence increases when the distal shield is high.
Genus Mazaganella Bown, 1987
{low to moderately high rim, dark shields (bright inner cycle in M. protensa); central-area axial cross, whichis broad and plate-like in M. pulla}
Genus Triscutum Dockerill, 1987
{distal shield is elevated; variable central-area structures, mainly grills and nets}

Family TUBODISCACEAE Bown & Rutledge fam. nov.
Type genus: Tubodiscus Thierstein, 1973.
Description: Elliptical placoliths composed of two narrow shields and a third, narrow, proximally-situated collar-cycle
which is variable in height. The central-area is broad and open; no central structures have yet been observed. The LM image
is dark, although the collar-cycle is brighter. Element curvature is dextrogyre in the distal shield and suture obliquity is
broadly dextral (clockwise). In the proximal shield these orientations are the same when viewed proximally. Suture
curvature in the collar-cycle is laevogyre when viewed proximally; element imbrication is anticlockwise (for T. verenae).
The crystallography of these coccoliths has not yet been determined.
Genus Manivitella Thierstein, 1971
{low proximal collar-cycle; large rim and wide ?vacant central-area}
Genus Tubodiscus Thierstein, 1973{high and birefringent proximal collar-cycle; wide ?vacant central-area}

1.2b. Imbricating placoliths (R-unit dominated)
Order WATZNAUERIALES Bown, 1987
Remarks: Includes placoliths (or modified placoliths) with shields formed from elements which display imbrication and inwhich the V-unit is usually reduced or vestigial, resulting in a high birefringence LM image. Element curvature is laevogyre
in the distal shield with broadly sinistral obliquity, and the same in the proximal shield when viewed proximally. Imbrication

Nanno classification, JNR 22

is clockwise in the distal shield, anticlockwise in the proximal shield, and clockwise in the V-unit cycle when developed(e.g. Bussonius).

Family WATZNAUERIACEAE Rood, Hay & Barnard, 1971
Description: Imbricating placoliths with two shields and a central-area which is usually closed or narrow and devoid ofcentral structures; or filled by a plug, spanned by bars, axial cross, or grill. The distal shield is superficially tricyclic,
composed of a broad outer-cycle of imbricating elements (R-unit) joined along kinked sutures; a narrow, median-cycle ofpeg-like elements (V-unit) and a narrow inner cycle (R-units). The two shields are actually formed from single R-unit
elements into which fit the narrow cycle of peg-like V-units (Young & Bown, 1991). The dominance of the R-units creates ahighly-birefringent LM image, in which the V-unit cycle appears only as a thin, dark line. The typical rim morphology is
modified in a number of genera, listed below (see also Figure 6).
Genus Cyclagelosphaera Noël, 1965
{circular shields; narrow or closed central-area}
Genus Lotharingius Noël, 1973 (= Bennocyclus Zweili & Grün, 1974 in Grün et al., 1974){central-area axial cross, with or without additional lateral bars}
Genus Watznaueria Reinhardt, 1964 (= Ellipsagelosphaera Noël, 1965; Caterella Black, 1971; Calolithus Noël,1965; Coptolithus Black, 1973; Margolatus Forchheimer, 1972; Actinosphaera Noël, 1965){central-area closed or narrow but may be spanned by transverse bar, bars or grill}

Modified Watznaueria-type rim
Genus Ansulasphaera Grün & Zweili, 1980{high, narrow, cylindrical proximal shield (anticlockwise imbrication); narrow, vacant central-area}?Genus Bibreviconus Rahman & Roth, 1991
{high, cylindrical morphology with a peg-like distal cycle; possibly the isolated central part of
Cyclagelosphaera deflandrei specimens which have lost the shields}
Genus Bussonius Goy, 1979
{V-unit cycle high and broad, forms a third, uppermost shield; central-area axial cross and lateral bars}?Genus Cylindralithus Bramlette & Martini, 1964
{earliest species, C. nudus, has watznaueriacean construction, but the shields are high (cf. Ansulasphaera)and differentiation between them is reduced (clockwise distal shield imbrication, anticlockwise proximal
shield imbrication; central-area vacant or with cross bars}?Genus Diazomatolithus Noël, 1965
{subcircular-circular with broad, vacant central-area; distal shield is monocyclic with radial sutures,proximal shield may be high and tapering with laevogyre element curvature, broadly sinistral obliquity andanticlockwise imbrication; low birefringence due to the expanded V-unit which forms the distal shield}[Genus Darwinilithus Watkins in Watkins & Bowdler, 1984]{possible junior synonym of Cylindralithus but tube-cycle elements protrude distally}

1.2c. Other placolith-like groups
Order ARKHANGELSKIALES Bown & Hampton ord. nov.
Description: Tiered 'placoliths' (see comments), with 3-5 closely appressed 'shields'. Central-area structures include
transverse bars with proximal net; axial or near-axial crosses with proximal net; and perforate plates crossed by axial ornear-axial sutures. LM images vary significantly, from predominantly dark in the Kamptneriaceae, to predominantly brightNanno classification, JNR 23

in the Arkhangelskiellaceae.
Comments: The Kamptneriaceae appears to have originated from loxolith coccoliths, and the tiered placolith rim structureis actually a modified loxolith construction (Hampton et al., in prep.). The earliest representatives of the family are only
slightly modified loxolith coccoliths. Such an evolutionary history has not yet been established for the Arkhangelskiellaceae.

Family ARKHANGELSKIELLACEAE Bukry, 1969 emend. Bown & Hampton
Description: Tiered 'placolith' coccoliths with central-areas spanned by axial crosses and grills, or filled by a perforate plate
divided by axial sutures. The 'shields' are typically bright in cross polarised light (rim dominated by R-unit) but bicyclic
images are also observed.
Genus Acaenolithus Black, 1973
{2-3 cycles form the distal shield, the inner cycle is broadest; bicyclic LM image, broad, bright inner cycleand narrow, dark outer cycle; broad central-area axial cross and grills, support boss or spine}
Genus Arkhangelskiella Vekshina, 1959
{1-2 distal shield cycles; bright, unicyclic LM image although darker towards outer edge; central-area
perforate plate with axial sutures}
Genus Aspidolithus Noël, 1969
{2-3 cycles form the distal shield, the inner cycle is broadest; indistinct bicyclic LM image, broad, brightinner cycle and narrow, darker outer cycle; central-area perforate plate with axial sutures, with no boss or
spine. Considered a junior synonym of Broinsonia by some}
Genus Broinsonia Bukry, 1969 (?= Aspidolithus Noël, 1969){as for Aspidolithus but if both genera are used, it is restricted to forms with broad central-area axial crosses
and grills}
Genus Thiersteinia Wise & Watkins in Wise, 1983
{as for Aspidolithus with perforate plate, axial struts and spine}

Family KAMPTNERIACEAE Bown & Hampton fam. nov.
Type genus: Kamptnerius Deflandre, 1959.
Description: Modified loxolith coccoliths, with distinctive LM images consisting of a narrow to moderately-broad rim witha narrow, dark outer cycle; a diagnostic, bright median cycle; and a dark, inner cycle. Central-area structures are generally
dark in LM, and may be a transverse bar, crossbars or plate, usually perforate; proximally-situated fine nets may be seen
when preservation is good. Rim structure varies from apparently typical loxolith (e.g. Thierstein, 1974: pl.4, figs 1, 9, 12) toplacolith-like, with at least three (pseudo) 'shields' (e.g. Thierstein, 1974: pl.7, figs 6, 8). The tiered nature is produced bylateral protrusions from the outer cycle of the loxolith wall. The V-unit cycle dominates the wall, but is penetrated by a thincycle of R-units, seen as a peg-like cycle in proximal view, and a median cycle in distal view, and it is this cycle which
creates the distinctive LM image.
[Genus Cribricatillus Black, 1973]{modified loxolith rim with Gartnerago-like LM image, central-area axial cross and net or bars; ?juniorsynonym of Gartnerago}?Genus Crucicribrum Black, 1973
{small ?tiered placoliths, with perforate central-area plate and axial cross and/or sutures}
Genus Gartnerago Bukry, 1969 (= ?Cribricatillus Black, 1973; Laffittius Noël, 1969){see family description. Central area structures - tranverse bar, broad axial cross, or perforate plate withaxial or near axial sutures; additional proximal nets or grills}

Nanno classification, JNR 24

Genus Kamptnerius Deflandre, 1959
{as for Gartnerago with an asymmetric rim flange forming a wing; reduced central-area plate}

1.3. Heterococcoliths of uncertain affinities
1.3a. Muroliths
Genus Clepsilithus Crux, 1987
{loxolith with 8 or more broad bars in the central-area}
Genus Laguncula Black, 1971{?loxoliths with bulbous/spherical, hollow 'spines'}
Genus Paralithella Lambert, 1993
{protoliths with central-area axial cross and longitudinal bars}
Genus Rectocorona Lambert, 1987
{protoliths with short, flaring distal-process}
Genus Tortolithus Crux, 1982
{muroliths with central-area closed by overlapping plates}?Genus Angulofenestrellithus Bukry, 1969
{narrow, bicyclic rim with broad perforate central-area plate (?3 cycles of holes)}

1.3b. Placoliths
Genus Boletuvelum Wind & Wise in Wise & Wind, 1977
{large, hollow, closed, flaring distal spine - see Biscutaceae}
Genus Chiastella Lambert, 1993{?tricyclic distal shield, diagonal cross}
Genus Diazomatolithus Noël, 1965
{subcircular-circular with broad, vacant central-area; distal shield is monocyclic with radial sutures,proximal shield may be high with dextrally imbricating elements; low birefringence - see Watznaueriaceae}
Genus Haqius Roth, 1978{(?elliptical)-circular with monocyclic distal shield formed from numerous dextrally imbricate elements, lowbirefringence LM image; narrow or closed central-area}
Genus Markalius Bramlette & Martini, 1964
{moderately birefringent interference figure with a bright tube-cycle; central-area narrow or closed}
Genus Prolatipatella Gartner, 1968
{narrow, ?tiered rim; thin, imperforate plate across wide central-area}
Genus Repagulum Forchheimer, 1972
{imbricating placoliths; monocyclic distal shield with numerous imbricate elements, distinctive but
inconspicuous, low birefringence, 'flaring' LM image; central-area spanned by ~16 radial bars}

2. HOLOCOCCOLITHS
Family CALYPTROSPHAERACEAE Boudreaux & Hay, 1969
Remarks: A strictly morphological taxonomic grouping which embraces coccolithophores which secrete holococcoliths.
Almost certainly includes taxa which also secrete heterococcoliths during non-motile phases and are then included in otherfamilies.

Nanno classification, JNR 25

The list below is probably overdivided, particularly the small forms which have rims formed from numerous blocks andhave only rarely been observed in the LM. However, a number of taxa are consistently recorded and applied inbiostratigraphy, e.g. Anfractus, Calculites and Lucianorhabdus.

2a. Cavate, Anfractus-like holococcoliths
Anfractus holococcoliths have been recorded inconsistently from Early Jurassic to mid-Cretaceous sediments (see Bown,
1993; Lambert, 1987).
Genus Anfractus Medd, 1979 emend. Bown, 1993
{elliptical, cavate (and usually septate), often bearing hollow spines; distal surface may be perforate; may
have internal buttresses}
Genus Stereorhabdus Lambert, 1987
{spine terminates in a stellate process}2b. Cavate with three to four proximal blocks, Lucianorhabdus-like
These forms are large and robust, and have been recorded consistently from Late Cretaceous sediments. They are typicallycavate but diagenesis commonly produces infilled cavities/spines and overgrown blocks.
Genus Acuturris Wind & Wise in Wise & Wind, 1977
{proximal plate of 3 blocks; tall, tapering spine}
Genus Calculites Prins & Sissingh in Sissingh, 1977
{proximal plate of 4 blocks; ridged and pitted distal surface; short, narrow, hollow spines}
Genus Isocrystallithus Verbeek, 1976 (= Owenia Crux, 1992){?cavate holococcoliths bearing moderately tall spines}
Genus Lucianorhabdus Deflandre, 1959
{proximal plate of four blocks; tall, hollow spine, often ridged or pitted; may be bulbous or curved}?Genus Orastrum Wind & Wise in Wise & Wind, 1977
{narrow rim surrounds central-area formed of 2-4 blocks; ?non-cavate, ?no spine}[Genus Owenia Crux, 1992]{bicyclic; narrow central-area spanned by arched bar. Junior synonym of Isocrystallithus}[Genus Semihololithus Perch-Nielsen, 1971]{the genus is probably a junior synonym of Daktylethra (Cenozoic). The Mesozoic species should probably
be assigned to Calculites or Lucianorhabdus}

2c. Rim formed from numerous small blocks with variable central structures
These forms are small and, in most cases, have only been described in the LM from a limited number of sites/samples;
mainly Late Cretaceous.
Genus Bifidalithus Varol, 1991
{narrow rim with central-area filled by two blocks divided by a transverse suture}
Genus Multipartis Risatti, 1973
{rim formed from ~7 triangular blocks; irregular blocks in the central-area}
Genus Munarinus Risatti, 1973
{rim formed from 4-12 blocks; central-area filled or spanned by disjunct bar/block}
Genus Octolithus Romein, 1979
{rim formed of 8 blocks, 4 large and 4 small}
Genus Okkolithus Wind & Wise in Wise & Wind, 1977

Nanno classification, JNR 26

{rim of ~20 blocks; central-area filled by 2 or more disjunct blocks}
Genus Ottavianus Risatti, 1973
{rim of 10-15 blocks, central-area spanned by ?conjunct bar/block}
Genus Pharus Wind & Wise in Wise & Wind, 1977
{elliptical, comprising one or two blocks, pierced by two round holes}
Genus Ramsaya Risatti, 1973
{rim of 12-14 blocks, central-area spanned by a narrow, dark bar}
Genus Russellia Risatti, 1973
{rim of 10-26 blocks; central perforation}
Genus Saepiovirgata Varol, 1991
{rim of 8-12 elements, with 2 longitudinally-oriented elongate blocks in the central-area}

2d. Others with recognisable coccolith morphology
Genus Coccosphaerida Lambert, 1987{high rim, formed from 3 layers of crystallites, ?distal surface covering}
Genus Lacunolithus Bown, 1993
{cavate, open proximal ring, flaring collar, domed distal covering}

2e. Non-coccolith morphology[Genus Athenagalea Hattner & Wise, 1980]{junior synonym of Petrobrasiella}
Genus Metadoga Wind & Cepek, 1979{conical-flask-shaped, with lid and internal partition}
Genus Petrobrasiella Troelsen & Quadros, 1971
{domed-shaped, pierced by holes/cavities}
Genus Pseudoconus Bown & Cooper, 1989
{solid, truncated-cone-shaped ?holococcolith with rectangular cross-section}
Genus Zebrashapka Covington & Wise, 1987
{solid, truncated-cone-shaped ?holococcolith, with distinct outer rim and banded core}

3. NANNOLITHS
Comments: The groups included here are mostly extinct taxa which had calcite tests within the size limits of calcareous
nannofossils but with morphologies which are distinct from either hetero- or holococcoliths.

Family BRAARUDOSPHAERACEAE Deflandre, 1947
Description: The extant species Braarudosphaera bigelowii has not been cultured but observations on live specimens
suggest that it is a haptophyte (J. Green, pers. comm., 1996). It has a cell-wall covering of twelve pentaliths, which form animperforate dodecahedron. The nannoliths are constructed from five segments which form a pentalith (a five-sided plate),
although stellate outlines are also common. C-axes are tangential to pentalith outline in plan view and individual crystal
units show laminar ultrastructure.
Genus Braarudosphaera Deflandre, 1947
{elements trapezoidal, sutures go to edges of the pentagon}?Genus Bukryaster Prins, 1971

Nanno classification, JNR 27

{stellate; sutures go to edges of the pentagon; ornament of 5 ridges and depressions}
Genus Micrantholithus Deflandre in Deflandre & Fert, 1954{sutures go to points of the pentagon; relationship between Neocomian and Cenozoic representatives
uncertain}
Genus Trapezopentus Wind & Cepek, 1979
{pentalith formed from 5 subrectangular elements surrounding a large central opening}

Family EOCONUSPHAERACEAE Kristan-Tollmann, 1988
Description: Nannoliths with a truncated-cone-like morphology constructed from an outer rim of thin, elements joined
along vertical sutures, and an inner core of numerous radial lamellae which protrude distally.
Comments: The three genera listed below have non-concurrent stratigraphic ranges but very closely comparable
morphologies and biogeographies (Bown & Cooper, 1989). The taxonomic validity of this grouping is thus uncertain. These
forms may prove to be modified heterococcoliths.
Genus Calcivascularis Wiegand, 1984 (= Mitrolithus jansae){inner core differentiated into proximal and distal parts, Early Jurassic}
Genus Conusphaera Trejo, 1969
{inner core differentiated longitudinally into 2 concentric cycles, L. Jurassic-E. Cretaceous}
Genus Eoconusphaera Jafar, 1983
{inner core formed from a single cycle of radial laths, Late Triassic}

Family GONIOLITHACEAE Deflandre, 1957
Description: Pentagonal plates with a thin rim and granular central-area plate.
Comments: Rare and sporadic stratigraphical distribution; K/T boundary survivor.
Genus Goniolithus Deflandre, 1957
{pentagonal plate with a distinct rim surrounding a mesh-like array of small crystals}

Family LAPIDEACASSACEAE Bown & Young fam. nov.
Type genus: Lapideacassis Black, 1971.
Description: Hemispherical to cylindrical nannoliths, with walls constructed from one to several cycles of thin elements,
enclosing a hollow central space; the nannolith tapers ?distally, and may have ?apical spines or processes.
Comments: Rare and sporadic stratigraphic distribution, but K/T boundary survivor.
Genus Lapideacassis Black, 1971 (= Scampanella Forchheimer & Stradner, 1973; Pervilithus Crux, 1981){see family description}[Genus Scampanella Forchheimer & Stradner, 1973]{has been used for forms with a single wall cycle; regarded here as a junior synonym of Lapideacassis}

Family MICRORHABDULACEAE Deflandre, 1963
Description: Elongate, rod-like nannoliths with a cruciform or circular cross-section, which generally taper at both ends.
Comments: The relationship between the four genera listed below is uncertain and this family may prove to bepolyphyletic.
Genus Lithraphidites Deflandre, 1963
{narrow rods with cruciform cross-section; may have expanded lateral blades}

Nanno classification, JNR 28

Genus Microrhabdulus Deflandre, 1959{~circular cross-section; complex construction from systematically arranged laths commonly creating a'chequered' LM image}
Genus Pseudolithraphidites Keupp, 1976
{nannoliths formed from 4-6 fused, circular rods; parallel sided}
Genus Pseudomicula Perch-Nielsen in Perch-Nielsen et al., 1978
{rod with massive, expanded mid-section}

Family NANNOCONACEAE Deflandre, 1959
Description: Conical, globular or cylindrical nannoliths composed entirely of spirally-arranged platelets, enclosing an axial
cavity or canal. C-axes arranged tangentially to central axis.
?Genus Faviconus Bralower in Bralower et al., 1989
{elongate, single or multiple columns of stacked platelets with thin axial canals}
Genus Nannoconus Kamptner, 1931
{see description of family}

Family POLYCYCLOLITHACEAE Forchheimer, 1972 emend. Varol, 1992
Description: Nannoliths composed of two vertically-appressed wall cycles and a central-area which may be closed, open
and vacant, or spanned by a diaphragm-like structure. Elements have tangential c-axis orientation.
Comments: This family has previously been used for a wide variety of nannoliths with radial, petaloid morphologies (e.g.
Perch-Nielsen, 1985). Varol (1992) redefined the family to include only those forms which appear to represent a clear
phylogenetic grouping, and this is followed below. Those forms which do not fall into this category are listed separately as
uncertain 'polycycloliths'.
Genus Eprolithus Stover, 1966 (= Polycyclolithus Forchheimer, 1968){5-9 petal-like, wall-cycle elements, moderately large median diaphragm}
Genus Farhania Varol, 1992
{16-24 rectangular, imbricating, wall-cycle elements, moderately large amedian diaphragm}
Genus Lithastrinus Stradner, 1962
{5-7 ray-like, strongly curved, wall-cycle elements, small median diaphragm}?Genus Micula Vekshina, 1959
{4 blocky, strongly twisted, wall-cycle elements, joined along sutures which go out to the points of the cube;
no central opening or diaphragm}
Genus Quadrum Prins & Perch-Nielsen in Manivit et al. 1977
{4-9 ray-like, wall-cycle elements. When cubiform, the elements are joined along sutures which go out tothe mid-point of the cube edges; no central opening or diaphragm}
Genus Radiolithus Stover, 1966 (= Rhombogyrus Black, 1973){9-16 brick-like, wall-cycle elements, large amedian diaphragm}
Genus Uniplanarius Hattner & Wise, 1980
{3 or 4 ray-like, wall-cycle elements, small median diaphragm}

Uncertain 'polycycloliths'
Genus Assipetra Thierstein, 1973
{solid, subrectangular-globular nannoliths formed from intergrown crystals}
Genus Hayesites Manivit, 1971 emend. Applegate et al. in Covington & Wise, 1987

Nanno classification, JNR 29

{stellate, with 6-11 dextrally imbricate rays; small subsidiary cycles and spines may be present; include only
H. albiensis and H. irregularis}
Genus Hexalithus Gardet, 1955
{form-taxon applied to 'hexaliths', i.e. hexagonal nannoliths formed from 6 elements}
Genus Perchnielsenella Watkins in Watkins & Bowdler, 1984{high, robust wall of ~30 imbricating elements, moderately large median diaphragm}
Genus Polycostella Thierstein, 1971
{circular to stellate, which may exhibit 6-8 radial ridges}
Genus Rucinolithus Stover, 1966
{stellate, formed from 5 or more ?sinistrally imbricating elements; small additional cycles may be present}
Genus Tegulalithus Crux, 1986
{single cycle of ~16 elements forms the wall; each end of the nannolith is covered by overlapping,concentric cycles of diamond-shaped elements, becoming smaller in diameter towards the centre, thus
forming a depression}

Family SCHIZOSPHAERELLACEAE Deflandre, 1959
Description: Hollow, spheroidal, bivalved nannoliths with walls constructed from a systematic geometric arrangement ofsmall, equidimensional crystallites.
Genus Schizosphaerella Deflandre & Dangeard, 1938{see family description}

Unclassified Mesozoic nannoliths
Genus Centosphaera Wind & Wise in Wise & Wind, 1977
{keeled sphere, constructed from hour glass-shaped crystallites. Considered a calcareous dinoflagellate by
Futterer, 1990}
Genus Ceratolithina Martini, 1967
{straight or hooked rods with lateral spurs and/or blades}
Genus Ceratolithoides Bramlette & Martini, 1964
{conical, arrowhead- or horseshoe-shaped nannoliths}
Genus Kokia Perch-Nielsen, 1988{rosette-shaped with 6 (8-10) or more rays (tangential c-axes); low birefringence}
Genus Liliasterites Stradner & Steinmetz, 1984
{3-rayed; long bifurcations give a 6-rayed appearance}
Genus Marthasterites Deflandre, 1959
{3-rayed; ray tips may bifurcate}
Genus Orthogonoides Wiegand, 1984
{orthogonally arranged 6-rayed nannolith}
Genus Prinsiosphaera Jafar, 1983
{solid, spherical nannolith formed from blocks of calcite laths}?Genus Watkinsia Covington, 1994
{large, narrowly elliptical, structureless base from which a broad, flat blade emerges}

Nanno classification, JNR 30

References
Black, M. & Barnes, B. 1959. The structure of Coccoliths from the English Chalk. Geological Magazine, 46(5): 311-333.
Bown, P.R. 1987. Taxonomy, biostratigraphy, and evolution of late Triassic-early Jurassic calcareous nannofossils. Special
Papers in Palaeontology, 38: 1-118.
Bown, P.R. 1993. New holococcoliths from the Toarcian-Aalenian (Jurassic) of northern Germany. Senckenbergiana
lethaea, 73: 407-419.
Bown, P.R. & Cooper, M.K.E. 1989. Conical calcareous nannofossil in the Mesozoic. In: J.A. Crux & S.E van Heck (eds).
Nannofossils and their applications . Ellis Horwood Limited, Chichester: 98-106.
Futterer, D.K. 1990. Distribution of calcareous dinoflagellates at the Cretaceous-Tertiary boundary of Queen Maud Rise,
Eastern Weddell Sea, Antarctica (ODP Leg 113). Proceedings of the ODP, Scientific Results, 113: 533-548.
Goy, G. 1981. Nannofossiles calcaires des schistes carton (Toarcien inférieur) du Bassin de Paris. Documents de la RCP
459, editions BRGM: 1-86.
Hattner, J.G. & Wise, S.W. 1980. Upper Cretaceous calcareous nannofossil biostratigraphy of South Carolina. South
Carolina Geology, 24: 41-117.
de Kaenel, E. & Bergen, J. 1993. New Early and Middle Jurassic coccolith taxa and biostratigraphy from the eastern protoAtlantic (Morocco, Portugal and DSDP Site 547B). Eclogae Geologicae Helvetiae, 86: 861-907.
Lambert, B. 1987. Nannofossiles calcaires de l'Albien supérieur et du Vraconnien du Cameroun meridian. Cahiers deMicropaléontologie, 2(2): 33-96.
Lambert, B. 1993. Nannofossiles calcaires de l'Albien supérieur et du Vraconnien du Cameroun méridional (Deuxième
Partie). Cahiers de Micropaléontologie, 8(2): 183-267.
Perch-Nielsen, K. 1985. Mesozoic calcareous nannofossils. In: H.M. Bolli, J.B. Saunders & K. Perch-Nielsen (eds).
Plankton Stratigraphy. Cambridge University Press: 329-426.
Thierstein, H.R. 1974. Calcareous nannoplankton - Leg 26, Deep Sea Drilling Project. IRDSDP, 26: 619-667.
Varol, O. 1992. Taxonomic revision of the Polycyclolithaceae and its contribution to Cretaceous biostratigraphy.
Newsletters in Stratigraphy, 27: 93-127.
Varol, O. & Girgis, M.H. 1994. New taxa and taxonomy of some Jurassic to Cretaceous calcareous nannofossils. Neues
Jahrbuch für Geologie und Paläontologie, Abhandlungen, 192: 221-253.
Young, J.R. & Bown, P.R. 1991. An ontogenetic sequence of coccoliths from the Late Jurassic Kimmeridge Clay of
England. Palaeontology, 34(4): 843-850.

Nanno classification, JNR 31

FIGURES

Figure 1: Initial development of the Eiffellithales. Range-bar conventions as follows: darker shading denotes welldocumented range, lighter shading denotes inconsistent or uncertain range; close-spacing indicates likely evolutionary
relationships and, when adjacent, these relationships are thought to be intergradational. Coccolith sketches are distal andside-views, darker-shaded rim-cycles indicate V-units, and lighter-shaded cycles R-units; central-area structures are given a
different shade.

Nanno classification, JNR 32

Nanno classification, JNR 33

Figure 3: Phylogeny of the Axopodorhabdaceae. Conventions as for Figure 1.

Nanno classification, JNR 34

Nanno classification, JNR 35

Figure 5: Stratigraphic distribution of the Cretarhabdaceae. The rim structure and phylogeny of this group are not wellunderstood. Shading of the rim does not indicate V- or R-unit.

Nanno classification, JNR 36

Figure 6: Phylogeny of the Watznaueriaceae. Range-bar conventions as for Figure 1.

Nanno classification, JNR 37

CENOZOIC CALCAREOUS NANNOPLANKTON CLASSIFICATION
Jeremy R. Young, Palaeontology Dept., NHM Cromwell Road, London, SW7 5BD, UK &Paul R. Bown, Dept. of Geological Sciences, UCL, Gower Street, London, WC1E 6BT, UK

Abstract
We present herein a revised three-level order-family-genus classification for Cenozoic calcareous nannoplankton. Two neworders (Zygodiscales, Prinsiales) and one new family (Calcidiscaceae) are introduced.

Introduction
The purpose and philosophy of this contribution are explained in the introductory section (Young & Bown, above). As in the
Mesozoic section (Bown & Young, above), a three-level order-family-genus classification is used, as far as seems
reasonable, based on current knowledge. In addition, a set of informal numbered groupings (1. Murolith coccoliths to 5c.
Nannoliths consisting of a single crystal-unit, and lacking radial symmetry) are used to provide a logical, but very possibly
artificial, organisation, particularly of families and genera incertae sedis. For completeness, living coccolithophorids areincluded, even when they have no known fossil record, this part of the classification being largely derived from Jordan &Green (1994) and Jordan et al. (1995). Genera with extant species are indicated by an asterisk *. If no fossil representatives
are known, a second asterisk is added **.

1. HETEROCOCCOLITHS
1.1. Murolith heterococcoliths
1.1a. Imbricating muroliths (loxoliths)
Order EIFFELLITHALES Rood, Hay & Barnard, 1971
This order is predominantly Mesozoic, see Bown & Young (above) for discussion.

Family CHIASTOZYGACEAE Rood, Hay & Barnard, 1973 emend. Varol & Girgis, 1994
The following two genera are known from both the Palaeocene and Maastrichtian and display the typical Zeugrhabdotustype rim-structure.
Genus Zeugrhabdotus Reinhardt, 1965
{The only Tertiary species, Z. sigmoides, has previously been included in Placozygus but shows typical
Zeugrhabdotus rim and central-area structure}
Genus Neocrepidolithus Romein, 1979
{broad, high rim with narrow or closed central-area which may be spanned by bars}

Order ZYGODISCALES Young & Bown ord. nov.
Description: Muroliths, and modified descendants, with an outer rim-cycle of V-units showing anticlockwise imbrication
and an inner rim-cycle showing clockwise imbrication - the opposite imbrication sense to Eiffellithales. This is a diverse
group but with clear evolutionary relationships (e.g. Romein, 1979; Aubry, 1989). Central-area structures include disjuncttransverse bars, diagonal crosses and perforate plates but no spines.
Comments: Often assumed to have evolved from the Eiffellithales, via Chiastozygus, Zeugrhabdotus or Placozygus.

Nanno classification, JNR 38

However, this is not based upon any directly observable transitions and the opposite imbrication directions of the rim-cycles
in the two orders makes this questionable. It is equally likely that the first member of the family, Neochiastozygus, evolved
from a quite different Cretaceous ancestor.
N.B. Regroupings - a conventional subdivision into three families is followed here, however:
1. The Pontosphaeraceae vs Zygodiscaceae subdivision is not obviously logical.
2. The Neococcolithes group arguably should be a separate group from the rest.
3. Grouping could be done via a new suborder or by making them all subfamilies of Pontosphaeraceae (this would have to
be used since it has priority).

Family HELICOSPHAERACEAE Black, 1971
Description: Extant species are motile, forming ellipsoidal coccospheres with a prominent flagellar opening. Coccoliths arearranged spirally round the coccosphere and may vary slightly in size and shape from the antapex to the flagellar pole. Outerrim (V-units) of the coccolith is modified into a helical flange, ending in a wing or spike. R-units form the baseplate and?extend to form a blanket of small elements. Central-area bars are conjunct, disjunct or absent.
Genus Helicosphaera* Kamptner, 1954 (= Helicopontosphaera Hay & Mohler, 1967){coccoliths with helical flange, subgroups can be recognised based on presence/absence of a disjunct bar,bar orientation, flange shape, etc.}

Family PONTOSPHAERACEAE Lemmermann, 1908
Description: Extant species apparently non-motile, coccospheres subspherical and may possess strongly-modified
equatorial coccoliths (Scyphosphaera). V-units form narrow outer rim-cycle. R-units form inner rim, baseplate and ?blanket.
No disjunct structures.
Genus Pontosphaera* Lohmann, 1902 (= Crassapontosphaera Boudreaux & Hay, 1969; Discolithina Loeblich &Tappan, 1963; Discolithus Huxley, 1868; Koczyia Boudreaux & Hay, 1969){central-area solid or with a variable number of pores}
Genus Scyphosphaera* Lohmann, 1902
{like Pontosphaera but with elevated equatorial coccoliths - lopadoliths [N.B. Calciopilleus andTintinnabuliformis are lopadolith-like coccoliths with apparently different ultrastructures, see incertae sedis
heterococcoliths]}
Genus Transversopontis Hay, Mohler & Wade, 1966
{central-area spanned by a conjunct bar, usually oblique}

Family ZYGODISCACEAE Hay & Mohler, 1967
A. Rim formed from well-developed V- and R-units, with opposite imbrication directions
Genus Jakubowskiella Varol, 1989
{open central-area}
Genus Lophodolithus Deflandre in Deflandre & Fert, 1954
{asymmetrical, often with disjunct bar}
Genus Neochiastozygus Perch-Nielsen, 1971
{with diagonal or asymmetric cross in central-area}
Genus Zygodiscus Bramlette & Sullivan, 1961
{symmetrical, with disjunct bar}Nanno classification, JNR 39

B. Rim formed from V-units; R-units vestigial or absent
Assignment of these genera to the Zygodiscaeae is based on imbrication direction of V-units, and putative evolutionary linkfrom Neochiastozygus to Neococcolithes.
Genus Neococcolithes Sujkowski, 1931 (= Heliorthus Bronnimann & Stradner, 1960; Indumentalithus Vekshina,
1959; Zygolithus Kamptner ex Matthes, 1956){H-shaped cross in central-area}
Genus Chiphragmalithus Bramlette & Sullivan, 1961
{High wall and well-developed central-area cross}? Genus Isthmolithus Deflandre, 1954
{parallelogram-shape, affinities to Zygodiscaceae uncertain, see Aubry (1988)}
Genus Nannotetrina Achuthan & Stradner, 1969 (= Nannotetraster Martini & Stradner 1960){X-shaped cross with no rim, probably derived from Chiphragmalithus or Neococcolithes by loss of rim (Perch-Nielsen,1985). N.B. Species were assigned to Nannotetraster until Acuthan & Stradner (1969) showed that it is a junior synonym ofMicula}1.1b. Other muroliths and planoliths
Comments: The structure of the three groups included here has not been fully worked out, and there is no direct fossil
evidence as to their phylogenetic relationships. Affinities between them have been inferred on the basis of central-areastructures which are characteristically composed of numerous concentric cycles of apparently disjunct elements, with
tangential c-axis orientations (T-units). The outermost of these central-area cycles usually consists of radial lath-shaped
elements which alternate around the rim with rim elements. This type of structure is shown by the three families included
here and so it has been inferred that they have a common ancestry. However the rim structures are markedly different in thethree so the apparent central-area similarities maybe misleading. All these groups are well known from the modern plankton
where they typically have medium-sized coccospheres covered with large numbers of small coccoliths (often <3 µm). Many
species show polymorphism. In the fossil record the small size of the coccoliths makes identification problematic.

Order STEPHANOLITHIALES Bown & Young ord. nov.
Family CALCIOSOLENIACEAE Kamptner, 1927
Description: Extant species are motile with elongate fusiform coccospheres and spine-bearing polar coccoliths. Coccoliths
are rhombic muroliths without flanges, usually termed scapholiths. The rim is predominantly formed of V-units, with small
R-units at the base. The central-area has a single lath-cycle, i.e. bars are formed of two laths, one from each side of thecentral-area.
Comments: This family is not recognised in many classifications of the extant coccolithophores, with the genera instead
being included in the Syracosphaeraceae, mainly due to similarities between central-area structures. We prefer to maintain it
as a separate family since the rim structure is not like that of typical Syracosphaeraceae. The group certainly extends into theMesozoic and may have evolved from the Stephanolithiaceae. In the LM, the rhombic shape makes it easy to recognisethese coccoliths but they are too small to be identified to a lower level and many palaeontologists assign all scapholiths tothe somewhat artificial species Scapholithus fossilis.
Genus Anoplosolenia* Deflandre, 1952
{no polar spines, coccoliths medium-sized - 4-7 µm}
Genus Calciosolenia* Gran, 1912 (= Acanthosolenia Bernard, 1939; ?= Scapholithus Deflandre, 1954)

Nanno classification, JNR 40

{with polar spines, coccoliths small - 2.5-3.5 µm}

Order SYRACOSPHAERALES Ostenfeld, 1899
Family SYRACOSPHAERACEAE Hay, 1977
Description: Extant species are motile, typically with elaborate coccospheres, often showing dithecatism (development ofdistinct inner and outer layers of coccoliths) and/or modified polar coccoliths. The endothecal (inner layer) coccoliths arenormally relatively conservative in form, typically muroliths with the rim-structure described above, a well-developed
central-area lath-cycle and variable inner central-area; they are often termed caneoliths. Exothecal coccoliths are much morevariable, including discoidal and dome-shaped forms (cyrtoliths).
Comments: These coccoliths are typically delicate and only rarely preserved. The recent tendency (e.g. Jordan et al., 1995),
pending a detailed revision, has been to combine the whole range of forms into the single genus Syracosphaera. Polarcoccoliths are often only mildly dimorphic, slightly smaller, more angular in shape and bear larger spines. In other cases
they are highly-modified, forming elaborate whorl structures. These forms are recognised as separate genera, as are a few
other distinctive forms. The fossil record of the family is poor but extends back into the Paleogene; fossil specimens arenormally assigned to Syracosphaera.

A. Genera with appendages
These genera have a whorl of appendages formed from highly modified coccoliths around either the apical (flagellar) or
antapical pole. They are all monothecate and the body coccoliths are muroliths with a single, weak, proximal flange. This
grouping is convenient but probably artificial and so we do not recommend describing a taxon based on it.
Genus Calciopappus** Gaarder & Ramsfjell, 1954 emend. Manton & Oates, 1983
{monothecate, with flangeless muroliths, apical coccoliths modified into elongate spines}
Genus Michaelsarsia** Gran, 1912 emend. Manton et al., 1984 (= Halopappus Lohmann, 1912){monothecate, with flangeless muroliths, apical appendages formed from a string of three highly- modified
coccoliths - osteoliths}
Genus Ophiaster** Gran, 1912 emend. Manton et al., 1984
{monothecate, with flangeless muroliths, antapical appendages formed from a string of several highly
modified coccoliths - osteoliths}

B. Genera without appendages
Genus Alisphaera** Heimdal, 1973
{monothecate, coccoliths are placolith-like, with asymmetrical flange bearing a spike or protrusion}
Genus Alveosphaera** Jordan & Young, 1990
{monothecate, coccoliths are elongate oblong muroliths, scapholith-like}
Genus Canistrolithus** Jordan & Chamberlain, 1993
{monothecate, coccoliths are elongate oblong muroliths, wall/rim weakly imbricate (anticlockwise) with
distal flange}
Genus Coronosphaera* Gaarder in Gaarder & Heimdal, 1977
{monothecate, coccoliths are flangeless muroliths, with strongly imbricate (anticlockwise) rims; placement
within this family is conventional but rim structure is anomalous}
Genus Syracosphaera* Lohmann, 1902

Nanno classification, JNR 41

{usually dithecate, exothecal coccoliths highly variable, endothecal coccoliths include muroliths with 1, 2 or
3 flanges and placolith-like form, apical coccoliths often have spines}[Genus Caneosphaera** Gaarder in Gaarder & Heimdal, 1977]{monothecate, coccoliths placolith-like, with asymmetrical flange; the included species are now usually
recombined in Syracosphaera}[Genus Deutschlandia* Lohmann, 1912]{exothecal coccoliths disc-shaped, the included species are now usually recombined in Syracosphaera}

Order RHABDOSPHAERALES Ostenfeld, 1899
Family RHABDOSPHAERACEAE Lemmermann, 1908
Description: Coccospheres may be motile or non-motile, typically they have spine-bearing and non-spine-bearing
coccoliths with similar shields. The spine-bearing coccoliths may be confined to the poles or distributed around thecoccosphere, greatly increasing its outer diameter. The coccoliths are disc-shaped (planoliths, see Young et al., in press)
with a distinct, slightly elevated rim. In modern species, this is formed of two cycles of elements: a lower/inner cycle
showing strong obliquity and an upper/outer cycle of simple non-imbricate elements (Kleijne, 1992). The upper/outer cycle
is formed of V-units, the orientation of the inner/lower cycle is unclear. Central-area T-unit cycles are well developed,
including both radial laths and usually a central spine or protrusion formed of numerous small elements with a spiralarrangement.
Comments: The spinose coccoliths are easy to spot in the LM and can usually be identified. In the Eocene, theRhabdosphaeraceae form a diverse and abundant group (Perch-Nielsen, 1985; Varol, 1989; Shafik, 1989).

Eocene genera
Rhabdoliths are common in the Eocene and show broadly similar structures and morphologies to modern forms but detailed
homologies with the extant genera are not clear. They are characterised by complex multicyclic shields and often multitiered central-structures. In addition, the outermost shield-cycle has far fewer elements than the inner shield-cycle. Forms
with cap-shaped protrusions appear particularly complex and Shafik (1989) differentiated numerous genera on structuraldetails, although these may prove to be oversplit (N.B. Shafik (1989) has priority over Varol (1989); official publication
dates are March 1989 vs May 1989, NHM library accession dates are August 1989 vs June 1990).
Genus Blackites Hay & Towe, 1962 emend Stradner & Edwards, 1968; Varol, 1989
{multicyclic rhabdolith with hollow spine and flaring collar}
Genera Cepekiella Roth, 1970; Discoturbella Roth, 1970; Naninfula Perch-Nielsen, 1968 emend Perch- Nielsen,
1971; Amitha Shafik, 1989; Notiocyrtolithus Shafik, 1989; Ommatolithus Shafik, 1989; Cruxia Varol, 1989
{multicyclic rhabdoliths with cap-shaped protrusions. Differential preservation and illustration modes (LM,
TEM, SEM) makes it impossible to rationalise the taxonomy on current data}
Genus Rhabdolithus Kamptner ex Deflandre in Grassé 1952
{with hollow spine, without flaring collar. Shield includes outer cycle with approximately half the number of
elements of the inner cycle. N.B. Many authors assign Eocene species to Rhabdosphaera but the structure ofthese forms appears significantly different to that of modern Rhabdosphaera}

Extant genera
Many species are too small to be readily identified by LM as isolated coccoliths and are rarely recorded as fossils. See

Nanno classification, JNR 42

Kleijne (1992) for review and detailed descriptions.
Genus Acanthoica* Lohmann, 1903 emend. Schiller, 1913 and Kleijne, 1992
{spines at poles only, coccoliths with radial T-cycle}
Genus Algirosphaera** Schlauder, 1945 emend. Norris, 1984
{spines modified into elongate domal or double-lipped (labiatiform) protrusion}
Genus Anacanthoica** Deflandre, 1952
{monomorphic, no spines, otherwise similar to Acanthoica}
Genus Cyrtosphaera* Kleijne, 1992
{vari-monomorphic, with domal or conical protrusions on all coccoliths, some species are strikingly similar
to the Eocene genera, but with simple shields}
Genus Discosphaera* Haeckel, 1894
{monomorphic, spines trumpet-like (salpingiform)}
Genus Palusphaera** Lecal, 1965 emend. Norris, 1984
{monomorphic, long spines}
Genus Rhabdosphaera* Haeckel, 1894 (= Rhabdolithus Kamptner ex Deflandre in Grassé, 1952){dimorphic with spine and non-spine bearing coccoliths, distributed around coccosphere. Used for many
fossil rhabdoliths}

1.2. Placolith heterococcoliths
Order PRINSIALES Young & Bown ord. nov.
Description: Extant species are based on non-motile heterococcolith-bearing stages. In addition, at least Emiliania huxleyi
and Gephyrocapsa oceanica have a motile scale-bearing stage. Coccospheres are subspherical and monomorphic.
Coccoliths are placoliths but unlike the Coccolithaceae, growth does not occur downward from the proto-coccolith ring. The
R-unit is always well developed, forming a proximal shield-element, two tube-elements with opposite senses of imbrication,and usually a central-area element. The V-unit is well developed in early forms, the Toweius-type structure, forming an
upper layer to the proximal shield, an outermost tube and the distal shield. In the Reticulofenestra-type structure, the V-unit
is virtually absent and the outer of the two R-unit tube-cycles is extended to form the distal shield. In both structure types,
the locus of the proto-coccolith ring is usually marked by a ring of slits. Central-area structures are always conjunct, being
formed from either the central-area element or the inner tube-element of the proximal shield.
Comment: The major difference between the Reticulofenestra-type structure and the Toweius-type structure forms a usefulbasis for subdividing this group (see Young & Bown, above, Figure 1), which was previously considered of family level andhas been variously referred to as the Noelaerhabdaceae and Prinsiaceae. Both family names are valid and so are used for thetwo emended families.

Family PRINSIACEAE Hay & Mohler, 1967 emend. (V-unit prominent)
Description: Genera with a prominent V-unit, and so a dark distal shield in LM (Toweius-type structure - see description oforder).
Comments: Confined to the Paleogene. They can be difficult to separate from small Coccolithus species in the LM, despite
the great structural differences; details of central-area structure and the extinction figure need to be used.
Genus Futyania Varol, 1989
{tube-elements extended to form a flower-like distal structure}
Genus Girgisia Varol, 1989

Nanno classification, JNR 43

{modified Toweius-type structure - central-area open, proximal shield shows low birefringence and appears
to be monocyclic but visible cycle must be an R-unit. Monospecific, G. gammation}?Genus Hornibrookina Edwards, 1973
{narrowly elliptical placoliths with central-area filled by large bars; proximal shield monocyclic; distal
shield bicyclic with inner cycle forming crown-like structure}
Genus Neobiscutum Varol, 1989
{earliest Danian forms, possibly with a simpler structure}
Genus Praeprinsius Varol & Jakubowski, 1989
{small early Prinsius/Neobiscutum intermediates}
Genus Prinsius Hay & Mohler, 1967
{elliptical, central-area closed by plate}
Genus Toweius Hay & Mohler, 1967
{circular to subcircular, central-area with variable number of pores}

Family NOELAERHABDACEAE Jerkovic, 1970 emend. (V-unit vestigial)
Description: Coccoliths with Reticulofenestra-type structure, i.e. V-unit vestigial, R-unit forms proximal shield, distal
shield, inner and outer tube-cycles, grill and any central-area structures; strongly birefringent (see also description of order
Young (1989)).
Genus Bekelithella Bona & Gal, 1985
{with flaring circlet of spines, formed from inner tube-elements, only recorded from Paratethys}?Genus Craterolithus Firth, 1988
{distal shield large and flaring upwards with 10-12 spines projecting down from it}
Genus Cribrocentrum Perch-Nielsen, 1971
{central-area partially closed by extensions of the inner tube-elements}
Genus Cyclicargolithus Bukry, 1971{(sub)circular with narrow central opening, often regarded as a junior synonym of Reticulofenestra}
Genus Dictyococcites Black, 1967
{central-area closed by plates formed from inner tube-cycle. N.B. Paleogene species such as D. scissura
appear distinct, but Neogene forms sometimes assigned to Dictyococcites are probably heavily calcified
varieties of Reticulofenestra}
Genus Emiliania* Hay & Mohler in Hay et al., 1967
{slits between all distal shield, and some proximal shield, elements}
Genus Gephyrocapsa* Kamptner, 1943
{with conjunct bar, formed from inner tube-elements}
Genus Noelaerhabdus Jerkovic, 1970
{with spine, formed from inner tube-elements, only recorded from Paratethys}
Genus Pseudoemiliania Gartner, 1969{slits between some distal shield elements}
Genus Reticulofenestra* Hay, Mohler & Wade, 1966 (= Apertapetra Hay, Mohler & Wade, 1966){lacking distinctive features, or with central-area partially closed by extensions of the inner tube- elements}[Bicolumnus Wei & Wise, 1990]{this morphotype is very similar to Pyrocyclus; it probably represents the isolated central-area and tubecycles of Dictyococcites}[Crenalithus Roth, 1973]

Nanno classification, JNR 44

{often used for small Reticulofenestra species, but the holotype is a junior synonym of Gephyrocapsa
oceanica}[Pyrocyclus Hay & Towe, 1962]{used for small 'species' with open central-area and no real shield development; these are probably early growth stages andbroken specimens of other reticulofenestrids, Young (in press)}.

Order COCCOSPHAERALES Haeckel, 1894 emend.
Comments: Extant species form non-motile heterococcolith-bearing stages. In Coccolithus and Calcidiscus, these are
known to alternate with motile holococcolith-bearing stages. The family Coccolithaceae is often used for all placoliths notplaced in the Prinsiales. Nonetheless, typical members of the family have a very characteristic rim-structure whilst manyother members have modified versions of this structure with sufficient similarity to strongly suggest a common origin. In
particular, growth occurs downward from the proto-coccolith ring which consequently becomes embedded within the rim.
Hence, on intact specimens, there is no obvious belt of alternating V- and R-elements, but such a belt is seen on specimens
where the proximal shield has been partially detached.

Family COCCOLITHACEAE Poche, 1913 emend. (Coccolithus-type rim)
Description: These have the Coccolithus-type rim-structure, as described in Young (1992). The V-unit forms both the distal
shield and the proximal layer of the central-area (= centro-proximal cycle). The R-unit forms the proximal shield and the
distal layer of the central-area (= centro-distal cycle). The proximal shield itself is bicyclic with distinct upper and lower
layers but these are both formed from the R-unit, unlike the Toweius-type structure. The central-area is often spanned by
disjunct structures and these are used to define genera.
Genus Bramletteius Gartner, 1969
{Cruciplacolithus-like base with very large monocrystalline 'paddle' or spine}
Genus Campylosphaera Kamptner, 1963
{strongly convex shield giving subrectangular outline, axial cross in central-area}
Genus Chiasmolithus Hay, Mohler & Wade, 1966
{diagonal, usually offset, cross in central-area, the bars of which show a median extinction line in XPL; thecentro-distal cycle forms a distinct collar around contact with V-units}
Genus Clausicoccus Prins, 1979
{typical Coccolithaceae rim (see SEMs in Varol (1989)), central-area wide, filled by disjunct plate withvariable number of perforations}
Genus Coccolithus* Schwartz, 1894 (= Coccosphaera Wallich, 1877; Ericsonia Black, 1964; Cyclolithus Kamptner,
1948){Central-area open or with a disjunct transverse bar}
Genus Cruciplacolithus Hay & Mohler in Hay et al., 1967
{axial or near-axial cross in central-area}
Genus Sullivania Varol, 1992
{diagonal, usually offset, cross in central-area, bars undivided in XPL. Centro-distal cycle does not form a
distinct collar}?Slightly modified Coccolithus-type rim
The following genera show strong similarities to the typical Coccolithaceae but probably have somewhat modified rims.

Nanno classification, JNR 45

[Genus Birkelundia Perch-Nielsen, 1971]{Perch-Nielsen (1971) placed three Eocene species in this genus on grounds that they had a monocyclic
proximal shield, however, none of them are unambiguous}
Genus Coronocyclus Hay, Mohler & Wade, 1966
{open ring-like coccolith without shields, elements of rim complexly intergrown, apparently with outer Vunit and inner R-unit. Included here in Coccolithaceae as structure suggests it is a neomorphic Coccolithus
derivative}
Genus Crassidiscus Okada, 1990
{monospecific, C. backmanii, large form with indistinct XPL image; SEM shows 3 tiers which may beequivalent to the three shield cycles of Coccolithus}
Genus Hughesius Varol, 1989
{like Clausicoccus but no inner bright cycle, so centro-distal R-unit element probably missing; ?proximal
shield also formed from V-unit}
Genus Solidopons Theodoridis, 1984
{narrow rimmed ?placolith with prominent arched bridge; extinction figure suggests affinities to
Coccolithus}

Family CALCIDISCACEAE Young & Bown fam. nov. (Calcidiscus-type rim)
Diagnosis: Coccosphaerales constans ex coccolithis cum R-unitis no nisi in proximo scuto. Coccosphaerales consisting of
coccoliths with R-units only in the proximal shield.
Description: Dominant phase of life-cycle, non-motile with placolith heterococcoliths. V-unit forms the distal shield andtube, extending to the proximal surface. R-unit forms the proximal shield. As in the Coccolithaceae, growth occurs
downward from the proto-coccolith ring which becomes embedded within the structure so that alternating V- and R-units
are only visible on specimens where the proximal shield has broken off. Distal shield sutures typically show laevogyral
curvature. The proximal shield is usually monocyclic with radial sutures; sometimes it is bicyclic due to the development ofa lower layer, with elements showing strong dextral obliquity (in proximal view). The connection between the proximal anddistal shields is weak and they frequently separate.
Comments: These genera have previously been included within the Coccolithaceae but the distinctively different structureappears to warrant classification in a separate family. The cytology of Umbilicosphaera is described by Inouye & Pienaar(1984).
Genus Calcidiscus* Kamptner, 1950 (= Cyclococcolithus, Cyclococcolithina, Cycloplacolithella, Cycloplacolithus,
Tiarolithus, Striatococcolithus Bukry, 1971){(sub)circular, central-area closed or narrow. Proximal shield elements often kinked, sometimes becoming bicyclic}
Genus Cryptococcolithus Gartner, 1992
{elliptical, proximal shield thin so coccolith is dark in XPL, central-area with non-birefringent perforate
plate}
Genus Cycloperfolithus Lehotayova & Priewalder, 1978
{sub-circular, central-area with non-birefringent perforate plate. Often regarded as a junior synonym of
Calcidiscus but proximal shield is described as bicyclic}
Genus Geminilithella Backman, 1980
{wide central-area and narrow rim (see Young (in press)) better regarded as a junior synonym ofUmbilicosphaera}
Genus Hayaster* Bukry, 1973

Nanno classification, JNR 46

{proximal shield diminutive, distal shield with straight radial sutures and angular ray ends, 9-13 elements}
Genus Oolithotus* Reinhardt in Cohen & Reinhardt, 1968
{asymmetrical, proximal shield elements show complex kinking, nearly becoming bicyclic, otherwise very
like Calcidiscus}
Genus Umbilicosphaera* Lohmann, 1902
{open central-area, distal shield elements show complex kinked sutures. Proximal shield monocyclic or
bicyclic}[Genus Striatococcolithus Bukry, 1971]{the only species, S. pacificanus, should probably be included in Calcidiscus}

Family PLEUROCHRYSIDACEAE Fresnel & Billard, 1991
This family is here included in the Coccosphaerales since the rim structure appears to be a simplified version of that of the
Coccolithaceae. It is monogeneric and possibly should be subsumed into the Coccolithaceae.
Genus Pleurochrysis** Pringsheim, 1955 (= Cricosphaera Braarud, 1960){Coccolithophore motile, neritic, coccosphere monomorphic. Coccoliths are narrow-shielded placoliths.
Tightly interlocked crystal-units, V-unit forms distal shield and tube. R-unit forms proximal shield and small
element on inside of tube - cricoliths}

Order WATZNAUERIALES Bown, 1987
Family WATZNAUERIACEAE Rood, Hay & Barnard, 1971
Genus Cyclagelosphaera Noël, 1965
{this predominantly Mesozoic genus persisted into the Danian; see Bown & Young (above)}1.3. Heterococcoliths of uncertain affinities
Family HYMENOMONADACEAE Senn, 1900
Description: Small littoral and fresh-water coccolithophores. Coccoliths are goblet-shaped muroliths with open central-area,
well-developed proximal flange, and a narrow distal flange or flaring end, entirely formed of a single cycle of <15 crystalunits (tremaliths). In Ochrosphaera, crystal-units have sub-vertical orientations. They differ from Pleurochrysidaceae by theabsence of a second cycle of units (i.e. R-units). References include Manton & Peterfi (1969), Braarud (1954) and Fresnel(1994).
Genus Hymenomonas** Stein, 1878
{freshwater and marine species, coccoliths with distal part flaring, elements have pointed ends}
Genus Ochrosphaera** Schussnig, 1930
{littoral, coccoliths with distinct distal flange}

Family PAPPOSPHAERACEAE Jordan & Young, 1990
Description: Family of minute, lightly-calcified coccolithophores, mainly known from high-latitudes, with holo- andheterococcolith phases (Thomsen et al., 1991). Heterococcoliths have a narrow murolith rim; +/- open central-area; tall,delicate spine supporting calyx of four plates (pappoliths). Holococcoliths tower-like, crystallites arranged in hexagonal or
triangular groups.
Genus Pappomonas** Manton & Oates, 1975
{heterococcospheres dimorphic, only circum-flagellar coccoliths have spines}

Nanno classification, JNR 47

Genus Papposphaera** Tangen, 1972
{heterococcospheres monomorphic, all bear spines}
Genus Trigonaspsis** Thomsen, 1980
{tower-like holococcoliths with triangular crystallite groups}[Genus Turrisphaera** Manton, Sutherland & Oates, 1976]{tower-like holococcoliths with hexagonal crystallite groups, = holococcolith phases of Pappomonas andPapposphaera spp.}

Possibly related weakly-calcified holococcoliths
Genus Balaniger ** Thomson & Oates, 1978
{coccoliths are organic scales with a few pyramidal ?crystallites}
Genus Calciarcus** Manton, Sutherland & Oates, 1977
{rhombohedral crystallites forming 4 struts ?with calcareous rim}
Genus Quaternariella** Thomsen, 1980
{coccoliths are organic scales with a few rhombohedral crystallites}

Possibly related weakly-calcified heterococcoliths
Genus Jomonlithus** Inouye & Chihara, 1983
{murolith coccoliths with Wigwamma-like rim, no central-area structures; partially calcified specimens show
beaded ultrastructure}
Genus Wigwamma** Manton, Sutherland & Oates, 1977
{simple rim and 'wigwam' of 3 or 4 struts}

Genera incertae sedis
A. Forms with a fossil record
This is a diverse group but all show typical heterococcolith structure, only Umbellosphaera and Neosphaera are extant.
Genus Calciopilleus Müller, 1974
{bell-shaped with external ridges}
Genus Conococcolithus Hay & Mohler, 1967
{poorly-documented conical placolith, one species, C. minutus, Palaeocene}
Genus Ellipsolithus Sullivan, 1964
{placolith morphology but structure anomalous}
Genus Hayella Gartner, 1969 (= Nannocorbis Müller, 1974, cf. Theodoridis, 1984){tube with two flanges, ?a modified placolith, formed of a single cycle of sub-vertical crystal-units}
Genus Ilselithina Stradner in Stradner & Adamiker, 1966
{modified placolith, distal shield reduced to a cycle of spines, formed of single cycle of steeply inclined
crystal-units}
Genus Markalius Bramlette & Martini, 1964
{moderately birefringent interference figure with a bright tube-cycle; central-area narrow or closed - detailsof structure uncertain}
Genus Neosphaera* Lecal-Schlauder, 1950 (= Craspedolithus Kamptner, 1963){open ring-like coccolith with proximal shield only, formed of single cycle of sub-vertical crystal- units;
possibly an alternate life-cycle stage of Ceratolithus (Alcober & Jordan, 1997)}
Genus Pedinocyclus Bukry & Bramlette, 1971 (nom subst pro Leptodiscus Bukry & Bramlette, 1969){poorly-documented circular placolith showing low birefringence}

Nanno classification, JNR 48

Genus Tintinnabuliformis Varol, 1991
{bell-shaped with apical horns}
Genus Umbellosphaera* Paasche in Markali & Paasche, 1955 (= Ellipsodiscoaster Boudreaux & Hay, 1969){? motile, placolith-like morphology with distal shield greatly extended, R-unit forms central-area, tube anddistal shield. Diminutive V-unit forms very narrow proximal shield. Distal shield is thin, except in some U.
tenuis, and so shows low birefringence; tube highly birefringent}

B. Recent genera
This diverse group of genera all show basic heterococcolith features (except perhaps Polycrater) and are mostly small andpoorly known. (N.B. Florisphaera is placed here among the nannoliths since it lacks any basal disc structure.)
Genus Gladiolithus* Jordan & Chamberlain, 1993
{basal disk of two elements supporting a long hexagonal-section spine; in LM isolated spine fragments
resemble long-thin Florisphaera profunda coccoliths}
Genus Polycrater** Manton & Oates, 1980
{coccoliths are aragonitic square-section cones, c.1µm across, very numerous on coccosphere}
Genus Turrilithus** Jordan et al., 1991
{narrow-rimmed placolith base, square-section flaring spine}
Genus Vexillarius** Jordan & Chamberlain, 1993
{small and rare, murolith base, square-section flaring spine}[Genus Thorosphaera** Ostenfeld, 1910]{very poorly-documented large coccolithophore, with tube-like coccoliths, possibly Scyphosphaera . N.B.
Thorosphaera flabellata is now placed in Gladiolithus}

2. HOLOCOCCOLITHS
Family CALYPTROSPHAERACEAE Boudreaux & Hay, 1969
Comments: Coccolithophores which are only known from a holococcolith-bearing stage are assigned to this family.
Holococcolith formation must be a rather precise biomineralisation process so this is probably not a polyphyletic grouping.
However, on present evidence it is likely that holo- and heterococcoliths are formed respectively during the haploid anddiploid life-cycle phases (Manton & Leedale, 1969; Rowson et al. 1986; Billard, 1994). It is quite likely that many more
holococcolith taxa will prove to have heterococcolith equivalents. So for the moment the holo- and heterococcolithclassifications should be seen as independent.
Holococcoliths have a very poor fossil record in the Quaternary and Neogene, perhaps largely because most of them are too
small (<2µm) to be easily preserved or identified. In the Paleogene, however, there are a number of large, distinctive
holococcolith taxa. It is therefore convenient to subdivide the holococcoliths into fossil (predominantly Paleogene) andextant groups. The Paleogene genera are divided into birefringent and non-birefringent groups, whilst the living group is
subdivided into monomorphic and dimorphic genera, following Kleijne (1991) and Jordan et al. (1995).

A. Non-birefringent fossil holococcoliths
Holococcoliths which are non-birefringent in plan view (i.e. all crystallites have vertical c-axes), predominantly Paleogene.
Genus Clathrolithus Deflandre, 1954
{large, discoidal with large perforations}
Genus Holodiscolithus Roth, 1970

Nanno classification, JNR 49

{discoidal with large perforations; one species H. macroporus occurs in the Neogene}
Genus Corannulus Stradner, 1962 (= Guttilithion Stradner, 1962; Diademopetra Hay, Mohler & Wade, 1966){discoidal with large central opening and marginal perforations or indentations}
Genus Peritrachelina Deflandre, 1952
{crescent-shaped in plan view}
Genus Orthozygus Bramlette & Wilcoxon, 1967
{basin shaped with a bridge (zygolith)}

B. Birefringent fossil holococcoliths
Holococcoliths showing birefringence in plan view, typically composed of several blocks with a narrow rim showing radial
crystallographic orientation.
Genus Daktylethra Gartner in Gartner & Bukry, 1969
{domal with exterior ridges and depressions. N.B. Calyptrosphaera pirus, a living species, is often assigned
to Daktylethra, but has a quite different morphology}
Genus Lanternithus Stradner, 1962
{subhexagonal in plan view}
Genus Octolithus Romein, 1979
{discoidal, formed of 4 large and 4 small blocks}
Genus Zygrhablithus Deflandre, 1959 (= Pseudozygrhablithus Haq, 1971; Sujkowskiella Hay, Mohler & Wade,
1966){discoidal base extended into tall spine}
Genus Quadrilateralis Varol, 1991
{quadrilateral rim of four blocks plus bridge}[Genus Semihololithus Perch-Nielsen, 1971]{defined as showing combined holococcolith and heterococcolith parts. Included Cenozoic species are
assignable to Daktylethra and Zygrhablithus}

C. Extant monomorphic holococcoliths
Genera with monomorphic coccospheres, i.e. only one type of coccolith developed.
Genus Kleijne, 1992
{chalice-shaped coccoliths - calcicaliths}
Genus Calyptrosphaera* Lohmann, 1902
{dome-shaped coccoliths - calyptroliths}
Genus Flosculosphaera** Jordan & Kleijne in Kleijne et al., 1991
{flaring tube-shaped coccoliths with distal cover - flosculoliths}
Genus Gliscolithus** Norris, 1985
{bulb-shaped coccoliths - gliscoliths}
Genus Homozygosphaera* Deflandre, 1952{basin-shaped coccoliths with bridge - zygoliths}
Genus Periphyllophora** Kamptner, 1937
{basin-shaped coccoliths with bridge extended into leaf-like process - helladoliths}
Genus Syracolithus** Deflandre, 1952
{disk-like coccoliths with variable number of depressions - laminoliths}

Nanno classification, JNR 50

D. Extant dimorphic holococcoliths
Genera with dimorphic coccospheres. These have body coccoliths of one type with a second type occurring apically, i.e.
around the flagellar opening.
Genus Anthosphaera Kamptner, 1937 emend. Kleijne, 1991
{calyptrolith body coccoliths and apical coccoliths with narrow basal ring and leaf-like process fragarioliths}
Genus Calyptrolithina Heimdal, 1982
{calyptrolith body coccoliths and apical zygoliths}
Genus Calyptrolithophora Heimdal in Heimdal & Gaarder, 1980
{calyptrolith body coccoliths and apical calyptroliths}
Genus Corisphaera Kamptner, 1937
{zygolith body coccoliths and apical zygoliths}
Genus Helladosphaera Kamptner, 1937
{zygolith body coccoliths and apical helladoliths}
Genus Poricalyptra Kleijne, 1991
{calyptrolith body coccoliths and apical helladoliths}
Genus Poritectolithus Kleijne, 1991
{zygolith body coccoliths and apical helladoliths}
Genus Sphaerocalyptra Deflandre, 1952{calyptrolith body coccoliths and apical calyptroliths}
Genus Zygosphaera Kamptner, 1936
{laminolith body coccoliths and apical laminoliths}

3. NANNOLITHSAs noted above (Young & Bown, above), the nannolith/heterococcolith divide is subjective. We include here all forms
which lack a distinct rim. Since V/R mode calcification has not been identified in any of these taxa we cannot be certain thatthey are directly related to the coccoliths. However they share with heterococcoliths the characteristics of being formed froma relatively low number of calcite crystals each of which has both its crystallographic orientation and morphology strongly
regulated. In addition, for all these, the distribution pattern suggests a planktonic origin.

3a. Nannoliths consisting of several crystal units and showing radial symmetry
Family BRAARUDOSPHAERACEAE Deflandre, 1947
Description: See Bown & Young (above).
Genus Braarudosphaera* Deflandre, 1947
{elements trapezoidal, sutures go to edges of the pentagon. Paleogene species are very diverse and include
conical forms}
Genus Micrantholithus Deflandre in Deflandre & Fert, 1954
{elements triangular, sutures go to vertices of the pentagon}
Genus Pemma Klump, 1953
{elements triangular, with a central knob, hole or depression}
Genus Pentaster Bybell & Gartner, 1972
{elements elongated into free rays}
Genus Quinquerhabdus Bukry & Bramlette, 1971
{pentalith greatly elevated}

Nanno classification, JNR 51

Family GONIOLITHACEAE Deflandre, 1957
Genus Goniolithus Deflandre, 1957
{pentagonal plate with a distinct rim surrounding a mesh-like array of small crystals. Rare and sporadic
stratigraphic distribution}

Family LAPIDEACASSACEAE Bown & Young fam. nov.
Genus Lapideacassis Black, 1971 (? = Scampanella Forchheimer & Stradner, 1973; Pervilithus Crux, 1981){see Bown & Young, above}

Genera incertae sedis
Genus Biantholithus Bramlette & Martini, 1964
{consist of 6-11 radial elements; LM birefringence is low and with an offset radial extinction cross; thenannoliths are concavo-convex and form spheres (Romein, 1979; Mai et al., 1994)}
Genus Nannoturba Müller, 1979
{mass of radiating rods, uncertain affinities}?Genus Nannotetrina Achuthan & Stradner, 1969 - see Zygodiscaceae
Genus Pseudotriquetrorhabdulus Wise in Wise & Constans, 1976
{rod-shaped with 6-12 laths; each lath is a separate crystal-unit with c-axis radial, relative to axis of the rod}

Order DISCOASTERALES Hay, 1977
We include in this order nannoliths with a structure of elements radiating from a common centre or axis. They all originate
in the Paleocene and evolutionary relationships between them have been suggested by, for example, Romein (1979) andPerch-Nielsen (1985). Nonetheless, it may represent a polyphyletic grouping.

Family DISCOASTERACEAE Tan, 1927
Description: Discoidal nannoliths of 3-40 elements radiating from a common centre. C-axes vertical, so nannoliths appear
dark in plane-polarised light. Some early forms also include a cycle of birefringent units.
Genus Catinaster Martini & Bramlette, 1963
{basket shaped, certainly derived from Discoaster, e.g. Peleo-Alampay et al. (in press)}
Genus Discoaster Tan, 1927 (= Agalmatoaster, Clavodiscoaster, Discoasteroides, Eudiscoaster, Gyrodiscoaster,
Heliodiscoaster, Hemidiscoaster, Radiodiscoaster, Truncodiscoaster, Turbodiscoaster){includes >100 species. The most obvious subdivision is into rosette-shaped species with >8 rays and starshaped species with <10 rays, and a number of other features parallel this subdivision. Formal classification
as proposed by Theodoridis (1984) into the genera Heliodiscoaster and Eudiscoaster has not, however,proven popular}

Family FASCICULITHACEAE Hay & Mohler, 1967
Description: Conical- or top-shaped nannoliths consisting of 10-30 wedge-shaped, radially-arranged elements. Apparently
distinct distal cycles are developed in some species but these probably are formed by kinking of the elements rather thanbeing new crystal-units. Suggested to be ancestral to the Heliolithaceae (Romein, 1979).
Genus Fasciculithus Bramlette & Sullivan, 1961{see family description}

Nanno classification, JNR 52

Family HELIOLITHACEAE Hay & Mohler, 1967
Description: Discoidal nannoliths consisting of at least two superposed cycles of crystal units. Suggested to be ancestral to
the Discoasteraceae (e.g. Romein, 1979).
Genus Bomolithus Roth, 1973
{in LM in plan view only the central column is bright}
Genus Heliolithus Bramlette & Sullivan, 1961 (= Bomolithus Roth, 1973){in LM in plan view the entire nannolith is bright}

Family SPHENOLITHACEAE Deflandre, 1952
Description: Conical-shaped nannoliths consisting of several superimposed cycles of elements all radiating from a common
point of origin. C-axes of the elements run along their length.
Genus Sphenolithus Deflandre in Grassé, 1952 (= Furcatolithus Martini, 1965; Sphenaster Wilcoxon, 1970){see family description}

3b. Nannoliths consisting of a single crystal-unit, showing radial symmetry
Family LITHOSTROMATIONACEAE Deflandre, 1959
Description: Relatively large (10-20µm) nannofossils, confined to epicontinental areas. Morphology is plate-like with rays
and interconnecting ridges. Strongly reminiscent of the internal spicules in actiniscid dinoflagellates. Show low
birefringence in plan view.
Genus Lithostromation Deflandre, 1942
{3-fold symmetry}
Genus Martiniaster Loeblich & Tappan, 1963 (= Coronaster Martini, 1961){12-rayed platelets}
Genus Trochoaster Klumpp, 1953
{6-fold symmetry}?Genus Isolithus Lyul'eva, 1989
{3-fold symmetry}
Genus Lacunolithus Lyul'eva, 1989
{platelet with 8 pairs of rays}

Genera incertae sedis
Genus Imperiaster Martini, 1970
{flattened tetrahedron}
Genus Rhomboaster Bramlette & Sullivan, 1961{+/- rhomboidal}
Genus Tribrachiatus Shamrai, 1963
{initially hexaradiate, formed by two superposed triplets of rays. Triplets rotate through evolution to become
parallel giving triradiate nannolith with bifurcate ray tips}
Genus Trochastrites Stradner, 1961
{planar triradiate nannolith with bifurcate ray tips, ?a holococcolith}[Marthasterites Deflandre, 1959]{this genus is now only used for Cretaceous forms but many species of Tribrachiatus were previously
included in it}

Nanno classification, JNR 53

3c. Nannoliths consisting of a single crystal unit, and lacking radial symmetry
Family CERATOLITHACEAE Norris, 1965
Description: Horseshoe-shaped nannoliths (ceratoliths) composed of a single crystal unit.
Comments: The extant species, Ceratolithus cristatus, occurs as a single nannolith which is apparently wrapped around thecell. Some cells also bear hoop-shaped coccoliths. Alcober & Jordan (1997) observed C. cristatus hoop-shaped coccoliths
inside Neosphaera coccolithomorpha coccospheres which suggests that ceratoliths may, like holococcoliths, be an alternate
phase of the life-cycle.
Genus Amaurolithus Gartner & Bukry, 1975
{c-axis vertical, nannolith dark in LM}
Genus Ceratolithus* Kamptner, 1950
{c-axis in plan of ceratolith, perpendicular to long axis, bright in LM}[Angulolithina Bukry, 1973]{angular V-shaped nannolith with c-axis parallel to length. These are of irregular morphology anddistribution, and may well be fragments of a larger non-haptophyte fossil}

Family TRIQUETRORHABDULACEAE Lipps, 1969
Description: Rod-shaped nannoliths formed of three blades (these may bear subsidiary ridges). The entire nannolith behaves
as one crystal-unit, crystallographic orientation varies between genera.
Genus Orthorhabdus Bramlette & Wilcoxon, 1967
{one blade wider than the other two, c-axis lies in plane of this blade, and perpendicular to the long- axis of
the nannolith}
Genus Triquetrorhabdulus Martini, 1965
{blades arranged at 120o to each other, uncurved, c-axis parallel to length; always shows strong
birefringence}unnamed Genus{T. rugosus and related species have structure distinct from Triquetrorhabdulus sensu Martini, 1965; one
blade narrower than the other two, c-axis lies in plane of this blade, and perpendicular to the long- axis of thenannolith; birefringence usually low (depends on how the specimen is lying); often curved. New genus to be
proposed (Varol & Young, in prep.)}[Pseudotriquetrorhabdulus Wise in Wise & Constans, 1976]{formed of a set of laths with radial c-axes and so included in radial nannoliths}

Genera incertae sedis
Genus Florisphaera* Okada & Honjo, 1973
{liths are small tapering plates which form artichoke-like coccospheres. C-axis parallel to the long axis of
the plate but birefringence is low due to small size. Very abundant. A peg-like structure on the base of somespecimens may indicate a second crystal-unit}
Genus Minylitha Bukry, 1973 emend. Theodoridis, 1984
{kite-shaped plate with raised rims on both sides, c-axis in plane of plate}Nanno classification, JNR 54

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